diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/RCU/RTFP.txt | 1784 | ||||
| -rw-r--r-- | Documentation/RCU/checklist.txt | 14 | ||||
| -rw-r--r-- | Documentation/RCU/stallwarn.txt | 87 | ||||
| -rw-r--r-- | Documentation/RCU/torture.txt | 33 | ||||
| -rw-r--r-- | Documentation/RCU/trace.txt | 36 | ||||
| -rw-r--r-- | Documentation/hwmon/w83627ehf | 9 | ||||
| -rw-r--r-- | Documentation/hwmon/zl6100 | 14 | ||||
| -rw-r--r-- | Documentation/lockup-watchdogs.txt | 63 | ||||
| -rw-r--r-- | Documentation/nmi_watchdog.txt | 83 | ||||
| -rw-r--r-- | Documentation/static-keys.txt | 286 | ||||
| -rw-r--r-- | Documentation/trace/ftrace.txt | 7 |
11 files changed, 2195 insertions, 221 deletions
diff --git a/Documentation/RCU/RTFP.txt b/Documentation/RCU/RTFP.txt index c43460dade0..7c1dfb19fc4 100644 --- a/Documentation/RCU/RTFP.txt +++ b/Documentation/RCU/RTFP.txt @@ -1,9 +1,10 @@ -Read the F-ing Papers! +Read the Fscking Papers! This document describes RCU-related publications, and is followed by the corresponding bibtex entries. A number of the publications may -be found at http://www.rdrop.com/users/paulmck/RCU/. +be found at http://www.rdrop.com/users/paulmck/RCU/. For others, browsers +and search engines will usually find what you are looking for. The first thing resembling RCU was published in 1980, when Kung and Lehman [Kung80] recommended use of a garbage collector to defer destruction @@ -160,7 +161,26 @@ which Mathieu Desnoyers is now maintaining [MathieuDesnoyers2009URCU] [MathieuDesnoyersPhD]. TINY_RCU [PaulEMcKenney2009BloatWatchRCU] made its appearance, as did expedited RCU [PaulEMcKenney2009expeditedRCU]. The problem of resizeable RCU-protected hash tables may now be on a path -to a solution [JoshTriplett2009RPHash]. +to a solution [JoshTriplett2009RPHash]. A few academic researchers are now +using RCU to solve their parallel problems [HariKannan2009DynamicAnalysisRCU]. + +2010 produced a simpler preemptible-RCU implementation +based on TREE_RCU [PaulEMcKenney2010SimpleOptRCU], lockdep-RCU +[PaulEMcKenney2010LockdepRCU], another resizeable RCU-protected hash +table [HerbertXu2010RCUResizeHash] (this one consuming more memory, +but allowing arbitrary changes in hash function, as required for DoS +avoidance in the networking code), realization of the 2009 RCU-protected +hash table with atomic node move [JoshTriplett2010RPHash], an update on +the RCU API [PaulEMcKenney2010RCUAPI]. + +2011 marked the inclusion of Nick Piggin's fully lockless dentry search +[LinusTorvalds2011Linux2:6:38:rc1:NPigginVFS], an RCU-protected red-black +tree using software transactional memory to protect concurrent updates +(strange, but true!) [PhilHoward2011RCUTMRBTree], yet another variant of +RCU-protected resizeable hash tables [Triplett:2011:RPHash], the 3.0 RCU +trainwreck [PaulEMcKenney2011RCU3.0trainwreck], and Neil Brown's "Meet the +Lockers" LWN article [NeilBrown2011MeetTheLockers]. + Bibtex Entries @@ -173,6 +193,14 @@ Bibtex Entries ,volume="5" ,number="3" ,pages="354-382" +,note="Available: +\url{http://portal.acm.org/citation.cfm?id=320619&dl=GUIDE,} +[Viewed December 3, 2007]" +,annotation={ + Use garbage collector to clean up data after everyone is done with it. + . + Oldest use of something vaguely resembling RCU that I have found. +} } @techreport{Manber82 @@ -184,6 +212,31 @@ Bibtex Entries ,number="82-01-01" ,month="January" ,pages="28" +,annotation={ + . + Superseded by Manber84. + . + Describes concurrent AVL tree implementation. Uses a + garbage-collection mechanism to handle concurrent use and deletion + of nodes in the tree, but lacks the summary-of-execution-history + concept of read-copy locking. + . + Keeps full list of processes that were active when a given + node was to be deleted, and waits until all such processes have + -terminated- before allowing this node to be reused. This is + not described in great detail -- one could imagine using process + IDs for this if the ID space was large enough that overlapping + never occurred. + . + This restriction makes this algorithm unsuitable for use in + systems comprised of long-lived processes. It also produces + completely unacceptable overhead in systems with large numbers + of processes. Finally, it is specific to AVL trees. + . + Cites Kung80, so not an independent invention, but the first + RCU-like usage that does not rely on an automatic garbage + collector. +} } @article{Manber84 @@ -195,6 +248,74 @@ Bibtex Entries ,volume="9" ,number="3" ,pages="439-455" +,annotation={ + Describes concurrent AVL tree implementation. Uses a + garbage-collection mechanism to handle concurrent use and deletion + of nodes in the tree, but lacks the summary-of-execution-history + concept of read-copy locking. + . + Keeps full list of processes that were active when a given + node was to be deleted, and waits until all such processes have + -terminated- before allowing this node to be reused. This is + not described in great detail -- one could imagine using process + IDs for this if the ID space was large enough that overlapping + never occurred. + . + This restriction makes this algorithm unsuitable for use in + systems comprised of long-lived processes. It also produces + completely unacceptable overhead in systems with large numbers + of processes. Finally, it is specific to AVL trees. +} +} + +@Conference{RichardRashid87a +,Author="Richard Rashid and Avadis Tevanian and Michael Young and +David Golub and Robert Baron and David Black and William Bolosky and +Jonathan Chew" +,Title="Machine-Independent Virtual Memory Management for Paged +Uniprocessor and Multiprocessor Architectures" +,Booktitle="{2\textsuperscript{nd} Symposium on Architectural Support +for Programming Languages and Operating Systems}" +,Publisher="Association for Computing Machinery" +,Month="October" +,Year="1987" +,pages="31-39" +,Address="Palo Alto, CA" +,note="Available: +\url{http://www.cse.ucsc.edu/~randal/221/rashid-machvm.pdf} +[Viewed February 17, 2005]" +,annotation={ + Describes lazy TLB flush, where one waits for each CPU to pass + through a scheduling-clock interrupt before reusing a given range + of virtual address. Does not describe how one determines that + all CPUs have in fact taken such an interrupt, though there are + no shortage of straightforward methods for accomplishing this. + . + Note that it does not make sense to just wait a fixed amount of + time, since a given CPU might have interrupts disabled for an + extended amount of time. +} +} + +@article{BarbaraLiskov1988ArgusCACM +,author = {Barbara Liskov} +,title = {Distributed programming in {Argus}} +,journal = {Commun. ACM} +,volume = {31} +,number = {3} +,year = {1988} +,issn = {0001-0782} +,pages = {300--312} +,doi = {http://doi.acm.org/10.1145/42392.42399} +,publisher = {ACM} +,address = {New York, NY, USA} +,annotation= { + At the top of page 307: "Conflicts with deposits and withdrawals + are necessary if the reported total is to be up to date. They + could be avoided by having total return a sum that is slightly + out of date." Relies on semantics -- approximate numerical + values sometimes OK. +} } @techreport{Hennessy89 @@ -216,6 +337,13 @@ Bibtex Entries ,year="1990" ,number="CS-TR-2222.1" ,month="June" +,annotation={ + Concurrent access to skip lists. Has both weak and strong search. + Uses concept of ``garbage queue'', but has no real way of cleaning + the garbage efficiently. + . + Appears to be an independent invention of an RCU-like mechanism. +} } @Book{Adams91 @@ -223,20 +351,15 @@ Bibtex Entries ,title="Concurrent Programming, Principles, and Practices" ,Publisher="Benjamin Cummins" ,Year="1991" +,annotation={ + Has a few paragraphs describing ``chaotic relaxation'', a + numerical analysis technique that allows multiprocessors to + avoid synchronization overhead by using possibly-stale data. + . + Seems like this is descended from yet another independent + invention of RCU-like function -- but this is restricted + in that reclamation is not necessary. } - -@phdthesis{HMassalinPhD -,author="H. Massalin" -,title="Synthesis: An Efficient Implementation of Fundamental Operating -System Services" -,school="Columbia University" -,address="New York, NY" -,year="1992" -,annotation=" - Mondo optimizing compiler. - Wait-free stuff. - Good advice: defer work to avoid synchronization. -" } @unpublished{Jacobson93 @@ -244,7 +367,13 @@ System Services" ,title="Avoid Read-Side Locking Via Delayed Free" ,year="1993" ,month="September" -,note="Verbal discussion" +,note="private communication" +,annotation={ + Use fixed time delay to approximate grace period. Very simple, + but subject to random memory corruption under heavy load. + . + Independent invention of RCU-like mechanism. +} } @Conference{AjuJohn95 @@ -256,6 +385,17 @@ System Services" ,Year="1995" ,pages="11-23" ,Address="New Orleans, LA" +,note="Available: +\url{https://www.usenix.org/publications/library/proceedings/neworl/full_papers/john.a} +[Viewed October 1, 2010]" +,annotation={ + Age vnodes out of the cache, and have a fixed time set by a kernel + parameter. Not clear that all races were in fact correctly handled. + Used a 20-minute time by default, which would most definitely not + be suitable during DoS attacks or virus scans. + . + Apparently independent invention of RCU-like mechanism. +} } @conference{Pu95a, @@ -301,31 +441,47 @@ Utilizing Execution History and Thread Monitoring" ,institution="US Patent and Trademark Office" ,address="Washington, DC" ,year="1995" -,number="US Patent 5,442,758 (contributed under GPL)" +,number="US Patent 5,442,758" ,month="August" +,annotation={ + Describes the parallel RCU infrastructure. Includes NUMA aspect + (structure of bitmap can reflect bus structure of computer system). + . + Another independent invention of an RCU-like mechanism, but the + "real" RCU this time! +} } @techreport{Slingwine97 ,author="John D. Slingwine and Paul E. McKenney" -,title="Method for maintaining data coherency using thread -activity summaries in a multicomputer system" +,title="Method for Maintaining Data Coherency Using Thread Activity +Summaries in a Multicomputer System" ,institution="US Patent and Trademark Office" ,address="Washington, DC" ,year="1997" -,number="US Patent 5,608,893 (contributed under GPL)" +,number="US Patent 5,608,893" ,month="March" +,pages="19" +,annotation={ + Describes use of RCU to synchronize data between a pair of + SMP/NUMA computer systems. +} } @techreport{Slingwine98 ,author="John D. Slingwine and Paul E. McKenney" -,title="Apparatus and method for achieving reduced overhead -mutual exclusion and maintaining coherency in a multiprocessor -system utilizing execution history and thread monitoring" +,title="Apparatus and Method for Achieving Reduced Overhead Mutual +Exclusion and Maintaining Coherency in a Multiprocessor System +Utilizing Execution History and Thread Monitoring" ,institution="US Patent and Trademark Office" ,address="Washington, DC" ,year="1998" -,number="US Patent 5,727,209 (contributed under GPL)" +,number="US Patent 5,727,209" ,month="March" +,annotation={ + Describes doing an atomic update by copying the data item and + then substituting it into the data structure. +} } @Conference{McKenney98 @@ -337,6 +493,15 @@ Problems" ,Year="1998" ,pages="509-518" ,Address="Las Vegas, NV" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/rclockpdcsproof.pdf} +[Viewed December 3, 2007]" +,annotation={ + Describes and analyzes RCU mechanism in DYNIX/ptx. Describes + application to linked list update and log-buffer flushing. + Defines 'quiescent state'. Includes both measured and analytic + evaluation. +} } @Conference{Gamsa99 @@ -349,18 +514,76 @@ Operating System Design and Implementation}" ,Year="1999" ,pages="87-100" ,Address="New Orleans, LA" +,note="Available: +\url{http://www.usenix.org/events/osdi99/full_papers/gamsa/gamsa.pdf} +[Viewed August 30, 2006]" +,annotation={ + Use of RCU-like facility in K42/Tornado. Another independent + invention of RCU. + See especially pages 7-9 (Section 5). +} +} + +@unpublished{RustyRussell2000a +,Author="Rusty Russell" +,Title="Re: modular net drivers" +,month="June" +,year="2000" +,day="23" +,note="Available: +\url{http://oss.sgi.com/projects/netdev/archive/2000-06/msg00250.html} +[Viewed April 10, 2006]" +,annotation={ + Proto-RCU proposal from Phil Rumpf and Rusty Russell. + Yet another independent invention of RCU. + Outline of algorithm to unload modules... + . + Appeared on net-dev mailing list. +} +} + +@unpublished{RustyRussell2000b +,Author="Rusty Russell" +,Title="Re: modular net drivers" +,month="June" +,year="2000" +,day="24" +,note="Available: +\url{http://oss.sgi.com/projects/netdev/archive/2000-06/msg00254.html} +[Viewed April 10, 2006]" +,annotation={ + Proto-RCU proposal from Phil Rumpf and Rusty Russell. + . + Appeared on net-dev mailing list. +} +} + +@unpublished{McKenney01b +,Author="Paul E. McKenney and Dipankar Sarma" +,Title="Read-Copy Update Mutual Exclusion in {Linux}" +,month="February" +,year="2001" +,note="Available: +\url{http://lse.sourceforge.net/locking/rcu/rcupdate_doc.html} +[Viewed October 18, 2004]" +,annotation={ + Prototypical Linux documentation for RCU. +} } @techreport{Slingwine01 ,author="John D. Slingwine and Paul E. McKenney" -,title="Apparatus and method for achieving reduced overhead -mutual exclusion and maintaining coherency in a multiprocessor -system utilizing execution history and thread monitoring" +,title="Apparatus and Method for Achieving Reduced Overhead Mutual +Exclusion and Maintaining Coherency in a Multiprocessor System +Utilizing Execution History and Thread Monitoring" ,institution="US Patent and Trademark Office" ,address="Washington, DC" ,year="2001" -,number="US Patent 5,219,690 (contributed under GPL)" +,number="US Patent 6,219,690" ,month="April" +,annotation={ + 'Change in mode' aspect of RCU. Can be thought of as a lazy barrier. +} } @Conference{McKenney01a @@ -372,14 +595,61 @@ Orran Krieger and Rusty Russell and Dipankar Sarma and Maneesh Soni" ,Year="2001" ,note="Available: \url{http://www.linuxsymposium.org/2001/abstracts/readcopy.php} -\url{http://www.rdrop.com/users/paulmck/rclock/rclock_OLS.2001.05.01c.pdf} +\url{http://www.rdrop.com/users/paulmck/RCU/rclock_OLS.2001.05.01c.pdf} [Viewed June 23, 2004]" -annotation=" -Described RCU, and presented some patches implementing and using it in -the Linux kernel. +,annotation={ + Described RCU, and presented some patches implementing and using + it in the Linux kernel. +} +} + +@unpublished{McKenney01f +,Author="Paul E. McKenney" +,Title="{RFC:} patch to allow lock-free traversal of lists with insertion" +,month="October" +,year="2001" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=100259266316456&w=2} +[Viewed June 23, 2004]" +,annotation=" + Memory-barrier and Alpha thread. 100 messages, not too bad... +" +} + +@unpublished{Spraul01 +,Author="Manfred Spraul" +,Title="Re: {RFC:} patch to allow lock-free traversal of lists with insertion" +,month="October" +,year="2001" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=100264675012867&w=2} +[Viewed June 23, 2004]" +,annotation=" + Suggested burying memory barriers in Linux's list-manipulation + primitives. " } +@unpublished{LinusTorvalds2001a +,Author="Linus Torvalds" +,Title="{Re:} {[Lse-tech]} {Re:} {RFC:} patch to allow lock-free traversal of lists with insertion" +,month="October" +,year="2001" +,note="Available: +\url{http://lkml.org/lkml/2001/10/13/105} +[Viewed August 21, 2004]" +} + +@unpublished{Blanchard02a +,Author="Anton Blanchard" +,Title="some RCU dcache and ratcache results" +,month="March" +,year="2002" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=101637107412972&w=2} +[Viewed October 18, 2004]" +} + @Conference{Linder02a ,Author="Hanna Linder and Dipankar Sarma and Maneesh Soni" ,Title="Scalability of the Directory Entry Cache" @@ -387,6 +657,10 @@ the Linux kernel. ,Month="June" ,Year="2002" ,pages="289-300" +,annotation=" + Measured scalability of Linux 2.4 kernel's directory-entry cache + (dcache), and measured some scalability enhancements. +" } @Conference{McKenney02a @@ -400,49 +674,76 @@ Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell" ,note="Available: \url{http://www.linux.org.uk/~ajh/ols2002_proceedings.pdf.gz} [Viewed June 23, 2004]" +,annotation=" + Presented and compared a number of RCU implementations for the + Linux kernel. +" } -@conference{Michael02a -,author="Maged M. Michael" -,title="Safe Memory Reclamation for Dynamic Lock-Free Objects Using Atomic -Reads and Writes" -,Year="2002" -,Month="August" -,booktitle="{Proceedings of the 21\textsuperscript{st} Annual ACM -Symposium on Principles of Distributed Computing}" -,pages="21-30" +@unpublished{Sarma02a +,Author="Dipankar Sarma" +,Title="specweb99: dcache scalability results" +,month="July" +,year="2002" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=102645767914212&w=2} +[Viewed June 23, 2004]" ,annotation=" - Each thread keeps an array of pointers to items that it is - currently referencing. Sort of an inside-out garbage collection - mechanism, but one that requires the accessing code to explicitly - state its needs. Also requires read-side memory barriers on - most architectures. + Compare fastwalk and RCU for dcache. RCU won. " } -@conference{Michael02b -,author="Maged M. Michael" -,title="High Performance Dynamic Lock-Free Hash Tables and List-Based Sets" -,Year="2002" -,Month="August" -,booktitle="{Proceedings of the 14\textsuperscript{th} Annual ACM -Symposium on Parallel -Algorithms and Architecture}" -,pages="73-82" +@unpublished{Barbieri02 +,Author="Luca Barbieri" +,Title="Re: {[PATCH]} Initial support for struct {vfs\_cred}" +,month="August" +,year="2002" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=103082050621241&w=2} +[Viewed: June 23, 2004]" ,annotation=" - Like the title says... + Suggested RCU for vfs\_shared\_cred. " } -@InProceedings{HerlihyLM02 -,author={Maurice Herlihy and Victor Luchangco and Mark Moir} -,title="The Repeat Offender Problem: A Mechanism for Supporting Dynamic-Sized, -Lock-Free Data Structures" -,booktitle={Proceedings of 16\textsuperscript{th} International -Symposium on Distributed Computing} -,year=2002 +@unpublished{Dickins02a +,author="Hugh Dickins" +,title="Use RCU for System-V IPC" +,year="2002" +,month="October" +,note="private communication" +} + +@unpublished{Sarma02b +,Author="Dipankar Sarma" +,Title="Some dcache\_rcu benchmark numbers" ,month="October" -,pages="339-353" +,year="2002" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=103462075416638&w=2} +[Viewed June 23, 2004]" +,annotation=" + Performance of dcache RCU on kernbench for 16x NUMA-Q and 1x, + 2x, and 4x systems. RCU does no harm, and helps on 16x. +" +} + +@unpublished{LinusTorvalds2003a +,Author="Linus Torvalds" +,Title="Re: {[PATCH]} small fixes in brlock.h" +,month="March" +,year="2003" +,note="Available: +\url{http://lkml.org/lkml/2003/3/9/205} +[Viewed March 13, 2006]" +,annotation=" + Linus suggests replacing brlock with RCU and/or seqlocks: + . + 'It's entirely possible that the current user could be replaced + by RCU and/or seqlocks, and we could get rid of brlocks entirely.' + . + Steve Hemminger responds by replacing them with RCU. +" } @article{Appavoo03a @@ -457,6 +758,20 @@ B. Rosenburg and M. Stumm and J. Xenidis" ,volume="42" ,number="1" ,pages="60-76" +,annotation=" + Use of RCU to enable hot-swapping for autonomic behavior in K42. +" +} + +@unpublished{Seigh03 +,author="Joseph W. {Seigh II}" +,title="Read Copy Update" +,Year="2003" +,Month="March" +,note="email correspondence" +,annotation=" + Described the relationship of the VM/XA passive serialization to RCU. +" } @Conference{Arcangeli03 @@ -470,6 +785,27 @@ Dipankar Sarma" ,year="2003" ,month="June" ,pages="297-310" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/rcu.FREENIX.2003.06.14.pdf} +[Viewed November 21, 2007]" +,annotation=" + Compared updated RCU implementations for the Linux kernel, and + described System V IPC use of RCU, including order-of-magnitude + performance improvements. +" +} + +@Conference{Soules03a +,Author="Craig A. N. Soules and Jonathan Appavoo and Kevin Hui and +Dilma {Da Silva} and Gregory R. Ganger and Orran Krieger and +Michael Stumm and Robert W. Wisniewski and Marc Auslander and +Michal Ostrowski and Bryan Rosenburg and Jimi Xenidis" +,Title="System Support for Online Reconfiguration" +,Booktitle="Proceedings of the 2003 USENIX Annual Technical Conference" +,Publisher="USENIX Association" +,year="2003" +,month="June" +,pages="141-154" } @article{McKenney03a @@ -481,6 +817,22 @@ Dipankar Sarma" ,volume="1" ,number="114" ,pages="18-26" +,note="Available: +\url{http://www.linuxjournal.com/article/6993} +[Viewed November 14, 2007]" +,annotation=" + Reader-friendly intro to RCU, with the infamous old-man-and-brat + cartoon. +" +} + +@unpublished{Sarma03a +,Author="Dipankar Sarma" +,Title="RCU low latency patches" +,month="December" +,year="2003" +,note="Message ID: 20031222180114.GA2248@in.ibm.com" +,annotation="dipankar/ct.2004.03.27/RCUll.2003.12.22.patch" } @techreport{Friedberg03a @@ -489,9 +841,14 @@ Dipankar Sarma" ,institution="US Patent and Trademark Office" ,address="Washington, DC" ,year="2003" -,number="US Patent 6,662,184 (contributed under GPL)" +,number="US Patent 6,662,184" ,month="December" ,pages="112" +,annotation=" + Applies RCU to a wildcard-search Patricia tree in order to permit + synchronization-free lookup. RCU is used to retain removed nodes + for a grace period before freeing them. +" } @article{McKenney04a @@ -503,6 +860,12 @@ Dipankar Sarma" ,volume="1" ,number="118" ,pages="38-46" +,note="Available: +\url{http://www.linuxjournal.com/node/7124} +[Viewed December 26, 2010]" +,annotation=" + Reader friendly intro to dcache and RCU. +" } @Conference{McKenney04b @@ -514,8 +877,83 @@ Dipankar Sarma" ,Address="Adelaide, Australia" ,note="Available: \url{http://www.linux.org.au/conf/2004/abstracts.html#90} -\url{http://www.rdrop.com/users/paulmck/rclock/lockperf.2004.01.17a.pdf} +\url{http://www.rdrop.com/users/paulmck/RCU/lockperf.2004.01.17a.pdf} [Viewed June 23, 2004]" +,annotation=" + Compares performance of RCU to that of other locking primitives + over a number of CPUs (x86, Opteron, Itanium, and PPC). +" +} + +@unpublished{Sarma04a +,Author="Dipankar Sarma" +,Title="{[PATCH]} {RCU} for low latency (experimental)" +,month="March" +,year="2004" +,note="\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=108003746402892&w=2}" +,annotation="Head of thread: dipankar/2004.03.23/rcu-low-lat.1.patch" +} + +@unpublished{Sarma04b +,Author="Dipankar Sarma" +,Title="Re: {[PATCH]} {RCU} for low latency (experimental)" +,month="March" +,year="2004" +,note="\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=108016474829546&w=2}" +,annotation="dipankar/rcuth.2004.03.24/rcu-throttle.patch" +} + +@unpublished{Spraul04a +,Author="Manfred Spraul" +,Title="[RFC] 0/5 rcu lock update" +,month="May" +,year="2004" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=108546407726602&w=2} +[Viewed June 23, 2004]" +,annotation=" + Hierarchical-bitmap patch for RCU infrastructure. +" +} + +@unpublished{Steiner04a +,Author="Jack Steiner" +,Title="Re: [Lse-tech] [RFC, PATCH] 1/5 rcu lock update: +Add per-cpu batch counter" +,month="May" +,year="2004" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=108551764515332&w=2} +[Viewed June 23, 2004]" +,annotation={ + RCU runs reasonably on a 512-CPU SGI using Manfred Spraul's patches, + which may be found at: + https://lkml.org/lkml/2004/5/20/49 (split vars into cachelines) + https://lkml.org/lkml/2004/5/22/114 (cpu_quiet() patch) + https://lkml.org/lkml/2004/5/25/24 (0/5) + https://lkml.org/lkml/2004/5/25/23 (1/5) + https://lkml.org/lkml/2004/5/25/265 (works for Jack) + https://lkml.org/lkml/2004/5/25/20 (2/5) + https://lkml.org/lkml/2004/5/25/22 (3/5) + https://lkml.org/lkml/2004/5/25/19 (4/5) + https://lkml.org/lkml/2004/5/25/21 (5/5) +} +} + +@Conference{Sarma04c +,Author="Dipankar Sarma and Paul E. McKenney" +,Title="Making {RCU} Safe for Deep Sub-Millisecond Response +Realtime Applications" +,Booktitle="Proceedings of the 2004 USENIX Annual Technical Conference +(FREENIX Track)" +,Publisher="USENIX Association" +,year="2004" +,month="June" +,pages="182-191" +,annotation=" + Describes and compares a number of modifications to the Linux RCU + implementation that make it friendly to realtime applications. +" } @phdthesis{PaulEdwardMcKenneyPhD @@ -529,17 +967,118 @@ Oregon Health and Sciences University" ,note="Available: \url{http://www.rdrop.com/users/paulmck/RCU/RCUdissertation.2004.07.14e1.pdf} [Viewed October 15, 2004]" +,annotation=" + Describes RCU implementations and presents design patterns + corresponding to common uses of RCU in several operating-system + kernels. +" } -@Conference{Sarma04c -,Author="Dipankar Sarma and Paul E. McKenney" -,Title="Making RCU Safe for Deep Sub-Millisecond Response Realtime Applications" -,Booktitle="Proceedings of the 2004 USENIX Annual Technical Conference -(FREENIX Track)" -,Publisher="USENIX Association" +@unpublished{PaulEMcKenney2004rcu:dereference +,Author="Dipankar Sarma" +,Title="{Re: RCU : Abstracted RCU dereferencing [5/5]}" +,month="August" ,year="2004" -,month="June" -,pages="182-191" +,note="Available: +\url{http://lkml.org/lkml/2004/8/6/237} +[Viewed June 8, 2010]" +,annotation=" + Introduce rcu_dereference(). +" +} + +@unpublished{JimHouston04a +,Author="Jim Houston" +,Title="{[RFC\&PATCH] Alternative {RCU} implementation}" +,month="August" +,year="2004" +,note="Available: +\url{http://lkml.org/lkml/2004/8/30/87} +[Viewed February 17, 2005]" +,annotation=" + Uses active code in rcu_read_lock() and rcu_read_unlock() to + make RCU happen, allowing RCU to function on CPUs that do not + receive a scheduling-clock interrupt. +" +} + +@unpublished{TomHart04a +,Author="Thomas E. Hart" +,Title="Master's Thesis: Applying Lock-free Techniques to the {Linux} Kernel" +,month="October" +,year="2004" +,note="Available: +\url{http://www.cs.toronto.edu/~tomhart/masters_thesis.html} +[Viewed October 15, 2004]" +,annotation=" + Proposes comparing RCU to lock-free methods for the Linux kernel. +" +} + +@unpublished{Vaddagiri04a +,Author="Srivatsa Vaddagiri" +,Title="Subject: [RFC] Use RCU for tcp\_ehash lookup" +,month="October" +,year="2004" +,note="Available: +\url{http://marc.theaimsgroup.com/?t=109395731700004&r=1&w=2} +[Viewed October 18, 2004]" +,annotation=" + Srivatsa's RCU patch for tcp_ehash lookup. +" +} + +@unpublished{Thirumalai04a +,Author="Ravikiran Thirumalai" +,Title="Subject: [patchset] Lockfree fd lookup 0 of 5" +,month="October" +,year="2004" +,note="Available: +\url{http://marc.theaimsgroup.com/?t=109144217400003&r=1&w=2} +[Viewed October 18, 2004]" +,annotation=" + Ravikiran's lockfree FD patch. +" +} + +@unpublished{Thirumalai04b +,Author="Ravikiran Thirumalai" +,Title="Subject: Re: [patchset] Lockfree fd lookup 0 of 5" +,month="October" +,year="2004" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=109152521410459&w=2} +[Viewed October 18, 2004]" +,annotation=" + Ravikiran's lockfree FD patch. +" +} + +@unpublished{PaulEMcKenney2004rcu:assign:pointer +,Author="Paul E. McKenney" +,Title="{[PATCH 1/3] RCU: \url{rcu_assign_pointer()} removal of memory barriers}" +,month="October" +,year="2004" +,note="Available: +\url{http://lkml.org/lkml/2004/10/23/241} +[Viewed June 8, 2010]" +,annotation=" + Introduce rcu_assign_pointer(). +" +} + +@unpublished{JamesMorris04a +,Author="James Morris" +,Title="{[PATCH 2/3] SELinux} scalability - convert {AVC} to {RCU}" +,day="15" +,month="November" +,year="2004" +,note="Available: +\url{http://marc.theaimsgroup.com/?l=linux-kernel&m=110054979416004&w=2} +[Viewed December 10, 2004]" +,annotation=" + James Morris posts Kaigai Kohei's patch to LKML. +" } @unpublished{JamesMorris04b @@ -550,6 +1089,85 @@ Oregon Health and Sciences University" ,note="Available: \url{http://www.livejournal.com/users/james_morris/2153.html} [Viewed December 10, 2004]" +,annotation=" + RCU helps SELinux performance. ;-) Made LWN. +" +} + +@unpublished{PaulMcKenney2005RCUSemantics +,Author="Paul E. McKenney and Jonathan Walpole" +,Title="{RCU} Semantics: A First Attempt" +,month="January" +,year="2005" +,day="30" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/rcu-semantics.2005.01.30a.pdf} +[Viewed December 6, 2009]" +,annotation=" + Early derivation of RCU semantics. +" +} + +@unpublished{PaulMcKenney2005e +,Author="Paul E. McKenney" +,Title="Real-Time Preemption and {RCU}" +,month="March" +,year="2005" +,day="17" +,note="Available: +\url{http://lkml.org/lkml/2005/3/17/199} +[Viewed September 5, 2005]" +,annotation=" + First posting showing how RCU can be safely adapted for + preemptable RCU read side critical sections. +" +} + +@unpublished{EsbenNeilsen2005a +,Author="Esben Neilsen" +,Title="Re: Real-Time Preemption and {RCU}" +,month="March" +,year="2005" +,day="18" +,note="Available: +\url{http://lkml.org/lkml/2005/3/18/122} +[Viewed March 30, 2006]" +,annotation=" + Esben Neilsen suggests read-side suppression of grace-period + processing for crude-but-workable realtime RCU. The downside + is indefinite grace periods...But this is OK for experimentation + and testing. +" +} + +@unpublished{TomHart05a +,Author="Thomas E. Hart and Paul E. McKenney and Angela Demke Brown" +,Title="Efficient Memory Reclamation is Necessary for Fast Lock-Free +Data Structures" +,month="March" +,year="2005" +,note="Available: +\url{ftp://ftp.cs.toronto.edu/csrg-technical-reports/515/} +[Viewed March 4, 2005]" +,annotation=" + Comparison of RCU, QBSR, and EBSR. RCU wins for read-mostly + workloads. ;-) +" +} + +@unpublished{JonCorbet2005DeprecateSyncKernel +,Author="Jonathan Corbet" +,Title="API change: synchronize_kernel() deprecated" +,month="May" +,day="3" +,year="2005" +,note="Available: +\url{http://lwn.net/Articles/134484/} +[Viewed May 3, 2005]" +,annotation=" + Jon Corbet describes deprecation of synchronize_kernel() + in favor of synchronize_rcu() and synchronize_sched(). +" } @unpublished{PaulMcKenney05a @@ -568,7 +1186,7 @@ Oregon Health and Sciences University" @conference{PaulMcKenney05b ,Author="Paul E. McKenney and Dipankar Sarma" -,Title="Towards Hard Realtime Response from the Linux Kernel on SMP Hardware" +,Title="Towards Hard Realtime Response from the {Linux} Kernel on {SMP} Hardware" ,Booktitle="linux.conf.au 2005" ,month="April" ,year="2005" @@ -578,6 +1196,103 @@ Oregon Health and Sciences University" [Viewed May 13, 2005]" ,annotation=" Realtime turns into making RCU yet more realtime friendly. + http://lca2005.linux.org.au/Papers/Paul%20McKenney/Towards%20Hard%20Realtime%20Response%20from%20the%20Linux%20Kernel/LKS.2005.04.22a.pdf +" +} + +@unpublished{PaulEMcKenneyHomePage +,Author="Paul E. McKenney" +,Title="{Paul} {E.} {McKenney}" +,month="May" +,year="2005" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/} +[Viewed May 25, 2005]" +,annotation=" + Paul McKenney's home page. +" +} + +@unpublished{PaulEMcKenneyRCUPage +,Author="Paul E. McKenney" +,Title="Read-Copy Update {(RCU)}" +,month="May" +,year="2005" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU} +[Viewed May 25, 2005]" +,annotation=" + Paul McKenney's RCU page. +" +} + +@unpublished{JosephSeigh2005a +,Author="Joseph Seigh" +,Title="{RCU}+{SMR} (hazard pointers)" +,month="July" +,year="2005" +,note="Personal communication" +,annotation=" + Joe Seigh announcing his atomic-ptr-plus project. + http://sourceforge.net/projects/atomic-ptr-plus/ +" +} + +@unpublished{JosephSeigh2005b +,Author="Joseph Seigh" +,Title="Lock-free synchronization primitives" +,month="July" +,day="6" +,year="2005" +,note="Available: +\url{http://sourceforge.net/projects/atomic-ptr-plus/} +[Viewed August 8, 2005]" +,annotation=" + Joe Seigh's atomic-ptr-plus project. +" +} + +@unpublished{PaulMcKenney2005c +,Author="Paul E.McKenney" +,Title="{[RFC,PATCH] RCU} and {CONFIG\_PREEMPT\_RT} sane patch" +,month="August" +,day="1" +,year="2005" +,note="Available: +\url{http://lkml.org/lkml/2005/8/1/155} +[Viewed March 14, 2006]" +,annotation=" + First operating counter-based realtime RCU patch posted to LKML. +" +} + +@unpublished{PaulMcKenney2005d +,Author="Paul E. McKenney" +,Title="Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.13-rc4-V0.7.52-01]" +,month="August" +,day="8" +,year="2005" +,note="Available: +\url{http://lkml.org/lkml/2005/8/8/108} +[Viewed March 14, 2006]" +,annotation=" + First operating counter-based realtime RCU patch posted to LKML, + but fixed so that various unusual combinations of configuration + parameters all function properly. +" +} + +@unpublished{PaulMcKenney2005rcutorture +,Author="Paul E. McKenney" +,Title="{[PATCH]} {RCU} torture testing" +,month="October" +,day="1" +,year="2005" +,note="Available: +\url{http://lkml.org/lkml/2005/10/1/70} +[Viewed March 14, 2006]" +,annotation=" + First rcutorture patch. " } @@ -591,22 +1306,39 @@ Distributed Processing Symposium" ,year="2006" ,day="25-29" ,address="Rhodes, Greece" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/hart_ipdps06.pdf} +[Viewed April 28, 2008]" +,annotation=" + Compares QSBR, HPBR, EBR, and lock-free reference counting. + http://www.cs.toronto.edu/~tomhart/perflab/ipdps06.tgz +" +} + +@unpublished{NickPiggin2006radixtree +,Author="Nick Piggin" +,Title="[patch 3/3] radix-tree: {RCU} lockless readside" +,month="June" +,day="20" +,year="2006" +,note="Available: +\url{http://lkml.org/lkml/2006/6/20/238} +[Viewed March 25, 2008]" ,annotation=" - Compares QSBR (AKA "classic RCU"), HPBR, EBR, and lock-free - reference counting. + RCU-protected radix tree. " } @Conference{PaulEMcKenney2006b ,Author="Paul E. McKenney and Dipankar Sarma and Ingo Molnar and Suparna Bhattacharya" -,Title="Extending RCU for Realtime and Embedded Workloads" +,Title="Extending {RCU} for Realtime and Embedded Workloads" ,Booktitle="{Ottawa Linux Symposium}" ,Month="July" ,Year="2006" ,pages="v2 123-138" ,note="Available: -\url{http://www.linuxsymposium.org/2006/index_2006.php} +\url{http://www.linuxsymposium.org/2006/view_abstract.php?content_key=184} \url{http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf} [Viewed January 1, 2007]" ,annotation=" @@ -614,6 +1346,37 @@ Suparna Bhattacharya" " } +@unpublished{WikipediaRCU +,Author="Paul E. McKenney and Chris Purcell and Algae and Ben Schumin and +Gaius Cornelius and Qwertyus and Neil Conway and Sbw and Blainster and +Canis Rufus and Zoicon5 and Anome and Hal Eisen" +,Title="Read-Copy Update" +,month="July" +,day="8" +,year="2006" +,note="Available: +\url{http://en.wikipedia.org/wiki/Read-copy-update} +[Viewed August 21, 2006]" +,annotation=" + Wikipedia RCU page as of July 8 2006. +" +} + +@Conference{NickPiggin2006LocklessPageCache +,Author="Nick Piggin" +,Title="A Lockless Pagecache in Linux---Introduction, Progress, Performance" +,Booktitle="{Ottawa Linux Symposium}" +,Month="July" +,Year="2006" +,pages="v2 249-254" +,note="Available: +\url{http://www.linuxsymposium.org/2006/view_abstract.php?content_key=184} +[Viewed January 11, 2009]" +,annotation=" + Uses RCU-protected radix tree for a lockless page cache. +" +} + @unpublished{PaulEMcKenney2006c ,Author="Paul E. McKenney" ,Title="Sleepable {RCU}" @@ -637,29 +1400,301 @@ Revised: ,day="18" ,year="2006" ,note="Available: -\url{http://www.nada.kth.se/~snilsson/public/papers/trash/trash.pdf} -[Viewed February 24, 2007]" +\url{http://www.nada.kth.se/~snilsson/publications/TRASH/trash.pdf} +[Viewed March 4, 2011]" ,annotation=" RCU-protected dynamic trie-hash combination. " } -@unpublished{ThomasEHart2007a -,Author="Thomas E. Hart and Paul E. McKenney and Angela Demke Brown and Jonathan Walpole" -,Title="Performance of memory reclamation for lockless synchronization" -,journal="J. Parallel Distrib. Comput." +@unpublished{ChristophHellwig2006RCU2SRCU +,Author="Christoph Hellwig" +,Title="Re: {[-mm PATCH 1/4]} {RCU}: split classic rcu" +,month="September" +,day="28" +,year="2006" +,note="Available: +\url{http://lkml.org/lkml/2006/9/28/160} +[Viewed March 27, 2008]" +} + +@unpublished{PaulEMcKenneyRCUusagePage +,Author="Paul E. McKenney" +,Title="{RCU} {Linux} Usage" +,month="October" +,year="2006" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/linuxusage.html} +[Viewed January 14, 2007]" +,annotation=" + Paul McKenney's RCU page showing graphs plotting Linux-kernel + usage of RCU. +" +} + +@unpublished{PaulEMcKenneyRCUusageRawDataPage +,Author="Paul E. McKenney" +,Title="Read-Copy Update {(RCU)} Usage in {Linux} Kernel" +,month="October" +,year="2006" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/linuxusage/rculocktab.html} +[Viewed January 14, 2007]" +,annotation=" + Paul McKenney's RCU page showing Linux usage of RCU in tabular + form, with links to corresponding cscope databases. +" +} + +@unpublished{GauthamShenoy2006RCUrwlock +,Author="Gautham R. Shenoy" +,Title="[PATCH 4/5] lock\_cpu\_hotplug: Redesign - Lightweight implementation of lock\_cpu\_hotplug" +,month="October" +,year="2006" +,day=26 +,note="Available: +\url{http://lkml.org/lkml/2006/10/26/73} +[Viewed January 26, 2009]" +,annotation=" + RCU-based reader-writer lock that allows readers to proceed with + no memory barriers or atomic instruction in absence of writers. + If writer do show up, readers must of course wait as required by + the semantics of reader-writer locking. This is a recursive + lock. +" +} + +@unpublished{JensAxboe2006SlowSRCU +,Author="Jens Axboe" +,Title="Re: [patch] cpufreq: mark \url{cpufreq_tsc()} as +\url{core_initcall_sync}" +,month="November" +,year="2006" +,day=17 +,note="Available: +\url{http://lkml.org/lkml/2006/11/17/56} +[Viewed May 28, 2007]" +,annotation=" + SRCU's grace periods are too slow for Jens, even after a + factor-of-three speedup. + Sped-up version of SRCU at http://lkml.org/lkml/2006/11/17/359. +" +} + +@unpublished{OlegNesterov2006QRCU +,Author="Oleg Nesterov" +,Title="Re: [patch] cpufreq: mark {\tt cpufreq\_tsc()} as +{\tt core\_initcall\_sync}" +,month="November" +,year="2006" +,day=19 +,note="Available: +\url{http://lkml.org/lkml/2006/11/19/69} +[Viewed May 28, 2007]" +,annotation=" + First cut of QRCU. Expanded/corrected versions followed. + Used to be OlegNesterov2007QRCU, now time-corrected. +" +} + +@unpublished{OlegNesterov2006aQRCU +,Author="Oleg Nesterov" +,Title="Re: [RFC, PATCH 1/2] qrcu: {"quick"} srcu implementation" +,month="November" +,year="2006" +,day=30 +,note="Available: +\url{http://lkml.org/lkml/2006/11/29/330} +[Viewed November 26, 2008]" +,annotation=" + Expanded/corrected version of QRCU. + Used to be OlegNesterov2007aQRCU, now time-corrected. +" +} + +@unpublished{EvgeniyPolyakov2006RCUslowdown +,Author="Evgeniy Polyakov" +,Title="Badness in postponing work" +,month="December" +,year="2006" +,day=05 +,note="Available: +\url{http://www.ioremap.net/node/41} +[Viewed October 28, 2008]" +,annotation=" + Using RCU as a pure delay leads to a 2.5x slowdown in skbs in + the Linux kernel. +" +} + +@inproceedings{ChrisMatthews2006ClusteredObjectsRCU +,author = {Matthews, Chris and Coady, Yvonne and Appavoo, Jonathan} +,title = {Portability events: a programming model for scalable system infrastructures} +,booktitle = {PLOS '06: Proceedings of the 3rd workshop on Programming languages and operating systems} +,year = {2006} +,isbn = {1-59593-577-0} +,pages = {11} +,location = {San Jose, California} +,doi = {http://doi.acm.org/10.1145/1215995.1216006} +,publisher = {ACM} +,address = {New York, NY, USA} +,annotation={ + Uses K42's RCU-like functionality to manage clustered-object + lifetimes. +}} + +@article{DilmaDaSilva2006K42 +,author = {Silva, Dilma Da and Krieger, Orran and Wisniewski, Robert W. and Waterland, Amos and Tam, David and Baumann, Andrew} +,title = {K42: an infrastructure for operating system research} +,journal = {SIGOPS Oper. Syst. Rev.} +,volume = {40} +,number = {2} +,year = {2006} +,issn = {0163-5980} +,pages = {34--42} +,doi = {http://doi.acm.org/10.1145/1131322.1131333} +,publisher = {ACM} +,address = {New York, NY, USA} +,annotation={ + Describes relationship of K42 generations to RCU. +}} + +# CoreyMinyard2007list_splice_rcu +@unpublished{CoreyMinyard2007list:splice:rcu +,Author="Corey Minyard and Paul E. McKenney" +,Title="{[PATCH]} add an {RCU} version of list splicing" +,month="January" +,year="2007" +,day=3 +,note="Available: +\url{http://lkml.org/lkml/2007/1/3/112} +[Viewed May 28, 2007]" +,annotation=" + Patch for list_splice_rcu(). +" +} + +@unpublished{PaulEMcKenney2007rcubarrier +,Author="Paul E. McKenney" +,Title="{RCU} and Unloadable Modules" +,month="January" +,day="14" +,year="2007" +,note="Available: +\url{http://lwn.net/Articles/217484/} +[Viewed November 22, 2007]" +,annotation=" + LWN article introducing the rcu_barrier() primitive. +" +} + +@unpublished{PeterZijlstra2007SyncBarrier +,Author="Peter Zijlstra and Ingo Molnar" +,Title="{[PATCH 3/7]} barrier: a scalable synchonisation barrier" +,month="January" +,year="2007" +,day=28 +,note="Available: +\url{http://lkml.org/lkml/2007/1/28/34} +[Viewed March 27, 2008]" +,annotation=" + RCU-like implementation for frequent updaters and rare readers(!). + Subsumed into QRCU. Maybe... +" +} + +@unpublished{PaulEMcKenney2007BoostRCU +,Author="Paul E. McKenney" +,Title="Priority-Boosting {RCU} Read-Side Critical Sections" +,month="February" +,day="5" +,year="2007" +,note="Available: +\url{http://lwn.net/Articles/220677/} +Revised: +\url{http://www.rdrop.com/users/paulmck/RCU/RCUbooststate.2007.04.16a.pdf} +[Viewed September 7, 2007]" +,annotation=" + LWN article introducing RCU priority boosting. +" +} + +@unpublished{PaulMcKenney2007QRCUpatch +,Author="Paul E. McKenney" +,Title="{[PATCH]} {QRCU} with lockless fastpath" +,month="February" +,year="2007" +,day=24 +,note="Available: +\url{http://lkml.org/lkml/2007/2/25/18} +[Viewed March 27, 2008]" +,annotation=" + Patch for QRCU supplying lock-free fast path. +" +} + +@article{JonathanAppavoo2007K42RCU +,author = {Appavoo, Jonathan and Silva, Dilma Da and Krieger, Orran and Auslander, Marc and Ostrowski, Michal and Rosenburg, Bryan and Waterland, Amos and Wisniewski, Robert W. and Xenidis, Jimi and Stumm, Michael and Soares, Livio} +,title = {Experience distributing objects in an SMMP OS} +,journal = {ACM Trans. Comput. Syst.} +,volume = {25} +,number = {3} +,year = {2007} +,issn = {0734-2071} +,pages = {6/1--6/52} +,doi = {http://doi.acm.org/10.1145/1275517.1275518} +,publisher = {ACM} +,address = {New York, NY, USA} +,annotation={ + Role of RCU in K42. +}} + +@conference{RobertOlsson2007Trash +,Author="Robert Olsson and Stefan Nilsson" +,Title="{TRASH}: A dynamic {LC}-trie and hash data structure" +,booktitle="Workshop on High Performance Switching and Routing (HPSR'07)" +,month="May" +,year="2007" +,note="Available: +\url{http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4281239} +[Viewed October 1, 2010]" +,annotation=" + RCU-protected dynamic trie-hash combination. +" +} + +@conference{PeterZijlstra2007ConcurrentPagecacheRCU +,Author="Peter Zijlstra" +,Title="Concurrent Pagecache" +,Booktitle="Linux Symposium" +,month="June" ,year="2007" -,note="To appear in J. Parallel Distrib. Comput. - \url{doi=10.1016/j.jpdc.2007.04.010}" +,address="Ottawa, Canada" +,note="Available: +\url{http://ols.108.redhat.com/2007/Reprints/zijlstra-Reprint.pdf} +[Viewed April 14, 2008]" +,annotation=" + Page-cache modifications permitting RCU readers and concurrent + updates. +" +} + +@unpublished{PaulEMcKenney2007whatisRCU +,Author="Paul E. McKenney" +,Title="What is {RCU}?" +,year="2007" +,month="07" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/whatisRCU.html} +[Viewed July 6, 2007]" ,annotation={ - Compares QSBR (AKA "classic RCU"), HPBR, EBR, and lock-free - reference counting. Journal version of ThomasEHart2006a. + Describes RCU in Linux kernel. } } @unpublished{PaulEMcKenney2007QRCUspin ,Author="Paul E. McKenney" -,Title="Using Promela and Spin to verify parallel algorithms" +,Title="Using {Promela} and {Spin} to verify parallel algorithms" ,month="August" ,day="1" ,year="2007" @@ -669,6 +1704,50 @@ Revised: ,annotation=" LWN article describing Promela and spin, and also using Oleg Nesterov's QRCU as an example (with Paul McKenney's fastpath). + Merged patch at: http://lkml.org/lkml/2007/2/25/18 +" +} + +@unpublished{PaulEMcKenney2007WG21DDOatomics +,Author="Paul E. McKenney and Hans-J. Boehm and Lawrence Crowl" +,Title="C++ Data-Dependency Ordering: Atomics and Memory Model" +,month="August" +,day="3" +,year="2007" +,note="Preprint: +\url{http://open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2664.htm} +[Viewed December 7, 2009]" +,annotation=" + RCU for C++, parts 1 and 2. +" +} + +@unpublished{PaulEMcKenney2007WG21DDOannotation +,Author="Paul E. McKenney and Lawrence Crowl" +,Title="C++ Data-Dependency Ordering: Function Annotation" +,month="September" +,day="18" +,year="2008" +,note="Preprint: +\url{http://open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2782.htm} +[Viewed December 7, 2009]" +,annotation=" + RCU for C++, part 2, updated many times. +" +} + +@unpublished{PaulEMcKenney2007PreemptibleRCUPatch +,Author="Paul E. McKenney" +,Title="[PATCH RFC 0/9] {RCU}: Preemptible {RCU}" +,month="September" +,day="10" +,year="2007" +,note="Available: +\url{http://lkml.org/lkml/2007/9/10/213} +[Viewed October 25, 2007]" +,annotation=" + Final patch for preemptable RCU to -rt. (Later patches were + to mainline, eventually incorporated.) " } @@ -686,10 +1765,46 @@ Revised: " } +@article{ThomasEHart2007a +,Author="Thomas E. Hart and Paul E. McKenney and Angela Demke Brown and Jonathan Walpole" +,Title="Performance of memory reclamation for lockless synchronization" +,journal="J. Parallel Distrib. Comput." +,volume={67} +,number="12" +,year="2007" +,issn="0743-7315" +,pages="1270--1285" +,doi="http://dx.doi.org/10.1016/j.jpdc.2007.04.010" +,publisher="Academic Press, Inc." +,address="Orlando, FL, USA" +,annotation={ + Compares QSBR, HPBR, EBR, and lock-free reference counting. + Journal version of ThomasEHart2006a. +} +} + +@unpublished{MathieuDesnoyers2007call:rcu:schedNeeded +,Author="Mathieu Desnoyers" +,Title="Re: [patch 1/2] {Linux} Kernel Markers - Support Multiple Probes" +,month="December" +,day="20" +,year="2007" +,note="Available: +\url{http://lkml.org/lkml/2007/12/20/244} +[Viewed March 27, 2008]" +,annotation=" + Request for call_rcu_sched() and rcu_barrier_sched(). +" +} + + ######################################################################## # # "What is RCU?" LWN series. # +# http://lwn.net/Articles/262464/ (What is RCU, Fundamentally?) +# http://lwn.net/Articles/263130/ (What is RCU's Usage?) +# http://lwn.net/Articles/264090/ (What is RCU's API?) @unpublished{PaulEMcKenney2007WhatIsRCUFundamentally ,Author="Paul E. McKenney and Jonathan Walpole" @@ -723,7 +1838,7 @@ Revised: 3. RCU is a Bulk Reference-Counting Mechanism 4. RCU is a Poor Man's Garbage Collector 5. RCU is a Way of Providing Existence Guarantees - 6. RCU is a Way of Waiting for Things to Finish + 6. RCU is a Way of Waiting for Things to Finish " } @@ -747,20 +1862,96 @@ Revised: # ######################################################################## + +@unpublished{SteveRostedt2008dyntickRCUpatch +,Author="Steven Rostedt and Paul E. McKenney" +,Title="{[PATCH]} add support for dynamic ticks and preempt rcu" +,month="January" +,day="29" +,year="2008" +,note="Available: +\url{http://lkml.org/lkml/2008/1/29/208} +[Viewed March 27, 2008]" +,annotation=" + Patch that prevents preemptible RCU from unnecessarily waking + up dynticks-idle CPUs. +" +} + +@unpublished{PaulEMcKenney2008LKMLDependencyOrdering +,Author="Paul E. McKenney" +,Title="Re: [PATCH 02/22 -v7] Add basic support for gcc profiler instrumentation" +,month="February" +,day="1" +,year="2008" +,note="Available: +\url{http://lkml.org/lkml/2008/2/2/255} +[Viewed October 18, 2008]" +,annotation=" + Explanation of compilers violating dependency ordering. +" +} + +@Conference{PaulEMcKenney2008Beijing +,Author="Paul E. McKenney" +,Title="Introducing Technology Into {Linux} Or: +Introducing your technology Into {Linux} will require introducing a +lot of {Linux} into your technology!!!" +,Booktitle="2008 Linux Developer Symposium - China" +,Publisher="OSS China" +,Month="February" +,Year="2008" +,Address="Beijing, China" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/TechIntroLinux.2008.02.19a.pdf} +[Viewed August 12, 2008]" +} + +@unpublished{PaulEMcKenney2008dynticksRCU +,Author="Paul E. McKenney and Steven Rostedt" +,Title="Integrating and Validating dynticks and Preemptable RCU" +,month="April" +,day="24" +,year="2008" +,note="Available: +\url{http://lwn.net/Articles/279077/} +[Viewed April 24, 2008]" +,annotation=" + Describes use of Promela and Spin to validate (and fix!) the + dynticks/RCU interface. +" +} + @article{DinakarGuniguntala2008IBMSysJ ,author="D. Guniguntala and P. E. McKenney and J. Triplett and J. Walpole" ,title="The read-copy-update mechanism for supporting real-time applications on shared-memory multiprocessor systems with {Linux}" ,Year="2008" -,Month="April" +,Month="April-June" ,journal="IBM Systems Journal" ,volume="47" ,number="2" -,pages="@@-@@" +,pages="221-236" ,annotation=" RCU, realtime RCU, sleepable RCU, performance. " } +@unpublished{LaiJiangshan2008NewClassicAlgorithm +,Author="Lai Jiangshan" +,Title="[{RFC}][{PATCH}] rcu classic: new algorithm for callbacks-processing" +,month="June" +,day="3" +,year="2008" +,note="Available: +\url{http://lkml.org/lkml/2008/6/2/539} +[Viewed December 10, 2008]" +,annotation=" + Updated RCU classic algorithm. Introduced multi-tailed list + for RCU callbacks and also pulling common code into + __call_rcu(). +" +} + @article{PaulEMcKenney2008RCUOSR ,author="Paul E. McKenney and Jonathan Walpole" ,title="Introducing technology into the {Linux} kernel: a case study" @@ -778,6 +1969,52 @@ Revised: } } +@unpublished{ManfredSpraul2008StateMachineRCU +,Author="Manfred Spraul" +,Title="[{RFC}, {PATCH}] state machine based rcu" +,month="August" +,day="21" +,year="2008" +,note="Available: +\url{http://lkml.org/lkml/2008/8/21/336} +[Viewed December 8, 2008]" +,annotation=" + State-based RCU. One key thing that this patch does is to + separate the dynticks handling of NMIs and IRQs. +" +} + +@unpublished{ManfredSpraul2008dyntickIRQNMI +,Author="Manfred Spraul" +,Title="Re: [{RFC}, {PATCH}] v4 scalable classic {RCU} implementation" +,month="September" +,day="6" +,year="2008" +,note="Available: +\url{http://lkml.org/lkml/2008/9/6/86} +[Viewed December 8, 2008]" +,annotation=" + Manfred notes a fix required to my attempt to separate irq + and NMI processing for hierarchical RCU's dynticks interface. +" +} + +@techreport{PaulEMcKenney2008cyclicRCU +,author="Paul E. McKenney" +,title="Efficient Support of Consistent Cyclic Search With Read-Copy Update" +,institution="US Patent and Trademark Office" +,address="Washington, DC" +,year="2008" +,number="US Patent 7,426,511" +,month="September" +,pages="23" +,annotation=" + Maintains an additional level of indirection to allow + readers to confine themselves to the desired snapshot of the + data structure. Only permits one update at a time. +" +} + @unpublished{PaulEMcKenney2008HierarchicalRCU ,Author="Paul E. McKenney" ,Title="Hierarchical {RCU}" @@ -793,6 +2030,21 @@ Revised: " } +@unpublished{PaulEMcKenney2009BloatwatchRCU +,Author="Paul E. McKenney" +,Title="Re: [PATCH fyi] RCU: the bloatwatch edition" +,month="January" +,day="14" +,year="2009" +,note="Available: +\url{http://lkml.org/lkml/2009/1/14/449} +[Viewed January 15, 2009]" +,annotation=" + Small-footprint implementation of RCU for uniprocessor + embedded applications -- and also for exposition purposes. +" +} + @conference{PaulEMcKenney2009MaliciousURCU ,Author="Paul E. McKenney" ,Title="Using a Malicious User-Level {RCU} to Torture {RCU}-Based Algorithms" @@ -816,15 +2068,17 @@ Revised: ,year="2009" ,note="Available: \url{http://lkml.org/lkml/2009/2/5/572} -\url{git://lttng.org/userspace-rcu.git} +\url{http://lttng.org/urcu} [Viewed February 20, 2009]" ,annotation=" Mathieu Desnoyers's user-space RCU implementation. git://lttng.org/userspace-rcu.git + http://lttng.org/cgi-bin/gitweb.cgi?p=userspace-rcu.git + http://lttng.org/urcu " } -@unpublished{PaulEMcKenney2009BloatWatchRCU +@unpublished{PaulEMcKenney2009LWNBloatWatchRCU ,Author="Paul E. McKenney" ,Title="{RCU}: The {Bloatwatch} Edition" ,month="March" @@ -852,14 +2106,29 @@ Revised: " } -@unpublished{JoshTriplett2009RPHash +@unpublished{PaulEMcKenney2009fastRTRCU +,Author="Paul E. McKenney" +,Title="[{PATCH} {RFC} -tip 0/4] {RCU} cleanups and simplified preemptable {RCU}" +,month="July" +,day="23" +,year="2009" +,note="Available: +\url{http://lkml.org/lkml/2009/7/23/294} +[Viewed August 15, 2009]" +,annotation=" + First posting of simple and fast preemptable RCU. +" +} + +@InProceedings{JoshTriplett2009RPHash ,Author="Josh Triplett" ,Title="Scalable concurrent hash tables via relativistic programming" ,month="September" ,year="2009" -,note="Linux Plumbers Conference presentation" +,booktitle="Linux Plumbers Conference 2009" ,annotation=" RP fun with hash tables. + See also JoshTriplett2010RPHash " } @@ -872,4 +2141,323 @@ Revised: ,note="Available: \url{http://www.lttng.org/pub/thesis/desnoyers-dissertation-2009-12.pdf} [Viewed December 9, 2009]" +,annotation={ + Chapter 6 (page 97) covers user-level RCU. +} +} + +@unpublished{RelativisticProgrammingWiki +,Author="Josh Triplett and Paul E. McKenney and Jonathan Walpole" +,Title="Relativistic Programming" +,month="September" +,year="2009" +,note="Available: +\url{http://wiki.cs.pdx.edu/rp/} +[Viewed December 9, 2009]" +,annotation=" + Main Relativistic Programming Wiki. +" +} + +@conference{PaulEMcKenney2009DeterministicRCU +,Author="Paul E. McKenney" +,Title="Deterministic Synchronization in Multicore Systems: the Role of {RCU}" +,Booktitle="Eleventh Real Time Linux Workshop" +,month="September" +,year="2009" +,address="Dresden, Germany" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/realtime/paper/DetSyncRCU.2009.08.18a.pdf} +[Viewed January 14, 2009]" +} + +@unpublished{PaulEMcKenney2009HuntingHeisenbugs +,Author="Paul E. McKenney" +,Title="Hunting Heisenbugs" +,month="November" +,year="2009" +,day="1" +,note="Available: +\url{http://paulmck.livejournal.com/14639.html} +[Viewed June 4, 2010]" +,annotation=" + Day-one bug in Tree RCU that took forever to track down. +" +} + +@unpublished{MathieuDesnoyers2009defer:rcu +,Author="Mathieu Desnoyers" +,Title="Kernel RCU: shrink the size of the struct rcu\_head" +,month="December" +,year="2009" +,note="Available: +\url{http://lkml.org/lkml/2009/10/18/129} +[Viewed December 29, 2009]" +,annotation=" + Mathieu proposed defer_rcu() with fixed-size per-thread pool + of RCU callbacks. +" +} + +@unpublished{MathieuDesnoyers2009VerifPrePub +,Author="Mathieu Desnoyers and Paul E. McKenney and Michel R. Dagenais" +,Title="Multi-Core Systems Modeling for Formal Verification of Parallel Algorithms" +,month="December" +,year="2009" +,note="Submitted to IEEE TPDS" +,annotation=" + OOMem model for Mathieu's user-level RCU mechanical proof of + correctness. +" +} + +@unpublished{MathieuDesnoyers2009URCUPrePub +,Author="Mathieu Desnoyers and Paul E. McKenney and Alan Stern and Michel R. Dagenais and Jonathan Walpole" +,Title="User-Level Implementations of Read-Copy Update" +,month="December" +,year="2010" +,url=\url{http://www.computer.org/csdl/trans/td/2012/02/ttd2012020375-abs.html} +,annotation=" + RCU overview, desiderata, semi-formal semantics, user-level RCU + usage scenarios, three classes of RCU implementation, wait-free + RCU updates, RCU grace-period batching, update overhead, + http://www.rdrop.com/users/paulmck/RCU/urcu-main-accepted.2011.08.30a.pdf + http://www.rdrop.com/users/paulmck/RCU/urcu-supp-accepted.2011.08.30a.pdf + Superseded by MathieuDesnoyers2012URCU. +" +} + +@inproceedings{HariKannan2009DynamicAnalysisRCU +,author = {Kannan, Hari} +,title = {Ordering decoupled metadata accesses in multiprocessors} +,booktitle = {MICRO 42: Proceedings of the 42nd Annual IEEE/ACM International Symposium on Microarchitecture} +,year = {2009} +,isbn = {978-1-60558-798-1} +,pages = {381--390} +,location = {New York, New York} +,doi = {http://doi.acm.org/10.1145/1669112.1669161} +,publisher = {ACM} +,address = {New York, NY, USA} +,annotation={ + Uses RCU to protect metadata used in dynamic analysis. +}} + +@conference{PaulEMcKenney2010SimpleOptRCU +,Author="Paul E. McKenney" +,Title="Simplicity Through Optimization" +,Booktitle="linux.conf.au 2010" +,month="January" +,year="2010" +,address="Wellington, New Zealand" +,note="Available: +\url{http://www.rdrop.com/users/paulmck/RCU/SimplicityThruOptimization.2010.01.21f.pdf} +[Viewed October 10, 2010]" +,annotation=" + TREE_PREEMPT_RCU optimizations greatly simplified the old + PREEMPT_RCU implementation. +" +} + +@unpublished{PaulEMcKenney2010LockdepRCU +,Author="Paul E. McKenney" +,Title="Lockdep-{RCU}" +,month="February" +,year="2010" +,day="1" +,note="Available: +\url{https://lwn.net/Articles/371986/} +[Viewed June 4, 2010]" +,annotation=" + CONFIG_PROVE_RCU, or at least an early version. +" +} + +@unpublished{AviKivity2010KVM2RCU +,Author="Avi Kivity" +,Title="[{PATCH} 37/40] {KVM}: Bump maximum vcpu count to 64" +,month="February" +,year="2010" +,note="Available: +\url{http://www.mail-archive.com/kvm@vger.kernel.org/msg28640.html} +[Viewed March 20, 2010]" +,annotation=" + Use of RCU permits KVM to increase the size of guest OSes from + 16 CPUs to 64 CPUs. +" +} + +@unpublished{HerbertXu2010RCUResizeHash +,Author="Herbert Xu" +,Title="bridge: Add core IGMP snooping support" +,month="February" +,year="2010" +,note="Available: +\url{http://kerneltrap.com/mailarchive/linux-netdev/2010/2/26/6270589} +[Viewed March 20, 2011]" +,annotation={ + Use a pair of list_head structures to support RCU-protected + resizable hash tables. +}} + +@article{JoshTriplett2010RPHash +,author="Josh Triplett and Paul E. McKenney and Jonathan Walpole" +,title="Scalable Concurrent Hash Tables via Relativistic Programming" +,journal="ACM Operating Systems Review" +,year=2010 +,volume=44 +,number=3 +,month="July" +,annotation={ + RP fun with hash tables. + http://portal.acm.org/citation.cfm?id=1842733.1842750 +}} + +@unpublished{PaulEMcKenney2010RCUAPI +,Author="Paul E. McKenney" +,Title="The {RCU} {API}, 2010 Edition" +,month="December" +,day="8" +,year="2010" +,note="Available: +\url{http://lwn.net/Articles/418853/} +[Viewed December 8, 2010]" +,annotation=" + Includes updated software-engineering features. +" +} + +@mastersthesis{AndrejPodzimek2010masters +,author="Andrej Podzimek" +,title="Read-Copy-Update for OpenSolaris" +,school="Charles University in Prague" +,year="2010" +,note="Available: +\url{https://andrej.podzimek.org/thesis.pdf} +[Viewed January 31, 2011]" +,annotation={ + Reviews RCU implementations and creates a few for OpenSolaris. + Drives quiescent-state detection from RCU read-side primitives, + in a manner roughly similar to that of Jim Houston. +}} + +@unpublished{LinusTorvalds2011Linux2:6:38:rc1:NPigginVFS +,Author="Linus Torvalds" +,Title="Linux 2.6.38-rc1" +,month="January" +,year="2011" +,note="Available: +\url{https://lkml.org/lkml/2011/1/18/322} +[Viewed March 4, 2011]" +,annotation={ + "The RCU-based name lookup is at the other end of the spectrum - the + absolute anti-gimmick. It's some seriously good stuff, and gets rid of + the last main global lock that really tends to hurt some kernel loads. + The dentry lock is no longer a big serializing issue. What's really + nice about it is that it actually improves performance a lot even for + single-threaded loads (on an SMP kernel), because it gets rid of some + of the most expensive parts of path component lookup, which was the + d_lock on every component lookup. So I'm seeing improvements of 30-50% + on some seriously pathname-lookup intensive loads." +}} + +@techreport{JoshTriplett2011RPScalableCorrectOrdering +,author = {Josh Triplett and Philip W. Howard and Paul E. McKenney and Jonathan Walpole} +,title = {Scalable Correct Memory Ordering via Relativistic Programming} +,year = {2011} +,number = {11-03} +,institution = {Portland State University} +,note = {\url{http://www.cs.pdx.edu/pdfs/tr1103.pdf}} +} + +@inproceedings{PhilHoward2011RCUTMRBTree +,author = {Philip W. Howard and Jonathan Walpole} +,title = {A Relativistic Enhancement to Software Transactional Memory} +,booktitle = {Proceedings of the 3rd USENIX conference on Hot topics in parallelism} +,series = {HotPar'11} +,year = {2011} +,location = {Berkeley, CA} +,pages = {1--6} +,numpages = {6} +,url = {http://www.usenix.org/event/hotpar11/tech/final_files/Howard.pdf} +,publisher = {USENIX Association} +,address = {Berkeley, CA, USA} +} + +@techreport{PaulEMcKenney2011cyclicparallelRCU +,author="Paul E. McKenney and Jonathan Walpole" +,title="Efficient Support of Consistent Cyclic Search With Read-Copy Update and Parallel Updates" +,institution="US Patent and Trademark Office" +,address="Washington, DC" +,year="2011" +,number="US Patent 7,953,778" +,month="May" +,pages="34" +,annotation=" + Maintains an array of generation numbers to track in-flight + updates and keeps an additional level of indirection to allow + readers to confine themselves to the desired snapshot of the + data structure. +" +} + +@inproceedings{Triplett:2011:RPHash +,author = {Triplett, Josh and McKenney, Paul E. and Walpole, Jonathan} +,title = {Resizable, Scalable, Concurrent Hash Tables via Relativistic Programming} +,booktitle = {Proceedings of the 2011 USENIX Annual Technical Conference} +,month = {June} +,year = {2011} +,pages = {145--158} +,numpages = {14} +,url={http://www.usenix.org/event/atc11/tech/final_files/atc11_proceedings.pdf} +,publisher = {The USENIX Association} +,address = {Portland, OR USA} +} + +@unpublished{PaulEMcKenney2011RCU3.0trainwreck +,Author="Paul E. McKenney" +,Title="3.0 and {RCU:} what went wrong" +,month="July" +,day="27" +,year="2011" +,note="Available: +\url{http://lwn.net/Articles/453002/} +[Viewed July 27, 2011]" +,annotation=" + Analysis of the RCU trainwreck in Linux kernel 3.0. +" +} + +@unpublished{NeilBrown2011MeetTheLockers +,Author="Neil Brown" +,Title="Meet the Lockers" +,month="August" +,day="3" +,year="2011" +,note="Available: +\url{http://lwn.net/Articles/453685/} +[Viewed September 2, 2011]" +,annotation=" + The Locker family as an analogy for locking, reference counting, + RCU, and seqlock. +" +} + +@article{MathieuDesnoyers2012URCU +,Author="Mathieu Desnoyers and Paul E. McKenney and Alan Stern and Michel R. Dagenais and Jonathan Walpole" +,Title="User-Level Implementations of Read-Copy Update" +,journal="IEEE Transactions on Parallel and Distributed Systems" +,volume={23} +,year="2012" +,issn="1045-9219" +,pages="375-382" +,doi="http://doi.ieeecomputersociety.org/10.1109/TPDS.2011.159" +,publisher="IEEE Computer Society" +,address="Los Alamitos, CA, USA" +,annotation={ + RCU overview, desiderata, semi-formal semantics, user-level RCU + usage scenarios, three classes of RCU implementation, wait-free + RCU updates, RCU grace-period batching, update overhead, + http://www.rdrop.com/users/paulmck/RCU/urcu-main-accepted.2011.08.30a.pdf + http://www.rdrop.com/users/paulmck/RCU/urcu-supp-accepted.2011.08.30a.pdf +} } diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt index bff2d8be1e1..5c8d7496809 100644 --- a/Documentation/RCU/checklist.txt +++ b/Documentation/RCU/checklist.txt @@ -180,6 +180,20 @@ over a rather long period of time, but improvements are always welcome! operations that would not normally be undertaken while a real-time workload is running. + In particular, if you find yourself invoking one of the expedited + primitives repeatedly in a loop, please do everyone a favor: + Restructure your code so that it batches the updates, allowing + a single non-expedited primitive to cover the entire batch. + This will very likely be faster than the loop containing the + expedited primitive, and will be much much easier on the rest + of the system, especially to real-time workloads running on + the rest of the system. + + In addition, it is illegal to call the expedited forms from + a CPU-hotplug notifier, or while holding a lock that is acquired + by a CPU-hotplug notifier. Failing to observe this restriction + will result in deadlock. + 7. If the updater uses call_rcu() or synchronize_rcu(), then the corresponding readers must use rcu_read_lock() and rcu_read_unlock(). If the updater uses call_rcu_bh() or diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 083d88cbc08..523364e4e1f 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -12,14 +12,38 @@ CONFIG_RCU_CPU_STALL_TIMEOUT This kernel configuration parameter defines the period of time that RCU will wait from the beginning of a grace period until it issues an RCU CPU stall warning. This time period is normally - ten seconds. + sixty seconds. -RCU_SECONDS_TILL_STALL_RECHECK + This configuration parameter may be changed at runtime via the + /sys/module/rcutree/parameters/rcu_cpu_stall_timeout, however + this parameter is checked only at the beginning of a cycle. + So if you are 30 seconds into a 70-second stall, setting this + sysfs parameter to (say) five will shorten the timeout for the + -next- stall, or the following warning for the current stall + (assuming the stall lasts long enough). It will not affect the + timing of the next warning for the current stall. - This macro defines the period of time that RCU will wait after - issuing a stall warning until it issues another stall warning - for the same stall. This time period is normally set to three - times the check interval plus thirty seconds. + Stall-warning messages may be enabled and disabled completely via + /sys/module/rcutree/parameters/rcu_cpu_stall_suppress. + +CONFIG_RCU_CPU_STALL_VERBOSE + + This kernel configuration parameter causes the stall warning to + also dump the stacks of any tasks that are blocking the current + RCU-preempt grace period. + +RCU_CPU_STALL_INFO + + This kernel configuration parameter causes the stall warning to + print out additional per-CPU diagnostic information, including + information on scheduling-clock ticks and RCU's idle-CPU tracking. + +RCU_STALL_DELAY_DELTA + + Although the lockdep facility is extremely useful, it does add + some overhead. Therefore, under CONFIG_PROVE_RCU, the + RCU_STALL_DELAY_DELTA macro allows five extra seconds before + giving an RCU CPU stall warning message. RCU_STALL_RAT_DELAY @@ -64,6 +88,54 @@ INFO: rcu_bh_state detected stalls on CPUs/tasks: { } (detected by 4, 2502 jiffi This is rare, but does happen from time to time in real life. +If the CONFIG_RCU_CPU_STALL_INFO kernel configuration parameter is set, +more information is printed with the stall-warning message, for example: + + INFO: rcu_preempt detected stall on CPU + 0: (63959 ticks this GP) idle=241/3fffffffffffffff/0 + (t=65000 jiffies) + +In kernels with CONFIG_RCU_FAST_NO_HZ, even more information is +printed: + + INFO: rcu_preempt detected stall on CPU + 0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 drain=0 . timer=-1 + (t=65000 jiffies) + +The "(64628 ticks this GP)" indicates that this CPU has taken more +than 64,000 scheduling-clock interrupts during the current stalled +grace period. If the CPU was not yet aware of the current grace +period (for example, if it was offline), then this part of the message +indicates how many grace periods behind the CPU is. + +The "idle=" portion of the message prints the dyntick-idle state. +The hex number before the first "/" is the low-order 12 bits of the +dynticks counter, which will have an even-numbered value if the CPU is +in dyntick-idle mode and an odd-numbered value otherwise. The hex +number between the two "/"s is the value of the nesting, which will +be a small positive number if in the idle loop and a very large positive +number (as shown above) otherwise. + +For CONFIG_RCU_FAST_NO_HZ kernels, the "drain=0" indicates that the +CPU is not in the process of trying to force itself into dyntick-idle +state, the "." indicates that the CPU has not given up forcing RCU +into dyntick-idle mode (it would be "H" otherwise), and the "timer=-1" +indicates that the CPU has not recented forced RCU into dyntick-idle +mode (it would otherwise indicate the number of microseconds remaining +in this forced state). + + +Multiple Warnings From One Stall + +If a stall lasts long enough, multiple stall-warning messages will be +printed for it. The second and subsequent messages are printed at +longer intervals, so that the time between (say) the first and second +message will be about three times the interval between the beginning +of the stall and the first message. + + +What Causes RCU CPU Stall Warnings? + So your kernel printed an RCU CPU stall warning. The next question is "What caused it?" The following problems can result in RCU CPU stall warnings: @@ -128,4 +200,5 @@ is occurring, which will usually be in the function nearest the top of that portion of the stack which remains the same from trace to trace. If you can reliably trigger the stall, ftrace can be quite helpful. -RCU bugs can often be debugged with the help of CONFIG_RCU_TRACE. +RCU bugs can often be debugged with the help of CONFIG_RCU_TRACE +and with RCU's event tracing. diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt index d67068d0d2b..375d3fb7143 100644 --- a/Documentation/RCU/torture.txt +++ b/Documentation/RCU/torture.txt @@ -69,6 +69,13 @@ onoff_interval CPU-hotplug operations regardless of what value is specified for onoff_interval. +onoff_holdoff The number of seconds to wait until starting CPU-hotplug + operations. This would normally only be used when + rcutorture was built into the kernel and started + automatically at boot time, in which case it is useful + in order to avoid confusing boot-time code with CPUs + coming and going. + shuffle_interval The number of seconds to keep the test threads affinitied to a particular subset of the CPUs, defaults to 3 seconds. @@ -79,6 +86,24 @@ shutdown_secs The number of seconds to run the test before terminating zero, which disables test termination and system shutdown. This capability is useful for automated testing. +stall_cpu The number of seconds that a CPU should be stalled while + within both an rcu_read_lock() and a preempt_disable(). + This stall happens only once per rcutorture run. + If you need multiple stalls, use modprobe and rmmod to + repeatedly run rcutorture. The default for stall_cpu + is zero, which prevents rcutorture from stalling a CPU. + + Note that attempts to rmmod rcutorture while the stall + is ongoing will hang, so be careful what value you + choose for this module parameter! In addition, too-large + values for stall_cpu might well induce failures and + warnings in other parts of the kernel. You have been + warned! + +stall_cpu_holdoff + The number of seconds to wait after rcutorture starts + before stalling a CPU. Defaults to 10 seconds. + stat_interval The number of seconds between output of torture statistics (via printk()). Regardless of the interval, statistics are printed when the module is unloaded. @@ -271,11 +296,13 @@ The following script may be used to torture RCU: #!/bin/sh modprobe rcutorture - sleep 100 + sleep 3600 rmmod rcutorture dmesg | grep torture: The output can be manually inspected for the error flag of "!!!". One could of course create a more elaborate script that automatically -checked for such errors. The "rmmod" command forces a "SUCCESS" or -"FAILURE" indication to be printk()ed. +checked for such errors. The "rmmod" command forces a "SUCCESS", +"FAILURE", or "RCU_HOTPLUG" indication to be printk()ed. The first +two are self-explanatory, while the last indicates that while there +were no RCU failures, CPU-hotplug problems were detected. diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt index 49587abfc2f..f6f15ce3990 100644 --- a/Documentation/RCU/trace.txt +++ b/Documentation/RCU/trace.txt @@ -33,23 +33,23 @@ rcu/rcuboost: The output of "cat rcu/rcudata" looks as follows: rcu_sched: - 0 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=545/1/0 df=50 of=0 ri=0 ql=163 qs=NRW. kt=0/W/0 ktl=ebc3 b=10 ci=153737 co=0 ca=0 - 1 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=967/1/0 df=58 of=0 ri=0 ql=634 qs=NRW. kt=0/W/1 ktl=58c b=10 ci=191037 co=0 ca=0 - 2 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=1081/1/0 df=175 of=0 ri=0 ql=74 qs=N.W. kt=0/W/2 ktl=da94 b=10 ci=75991 co=0 ca=0 - 3 c=20942 g=20943 pq=1 pgp=20942 qp=1 dt=1846/0/0 df=404 of=0 ri=0 ql=0 qs=.... kt=0/W/3 ktl=d1cd b=10 ci=72261 co=0 ca=0 - 4 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=369/1/0 df=83 of=0 ri=0 ql=48 qs=N.W. kt=0/W/4 ktl=e0e7 b=10 ci=128365 co=0 ca=0 - 5 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=381/1/0 df=64 of=0 ri=0 ql=169 qs=NRW. kt=0/W/5 ktl=fb2f b=10 ci=164360 co=0 ca=0 - 6 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=1037/1/0 df=183 of=0 ri=0 ql=62 qs=N.W. kt=0/W/6 ktl=d2ad b=10 ci=65663 co=0 ca=0 - 7 c=20897 g=20897 pq=1 pgp=20896 qp=0 dt=1572/0/0 df=382 of=0 ri=0 ql=0 qs=.... kt=0/W/7 ktl=cf15 b=10 ci=75006 co=0 ca=0 + 0 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=545/1/0 df=50 of=0 ql=163 qs=NRW. kt=0/W/0 ktl=ebc3 b=10 ci=153737 co=0 ca=0 + 1 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=967/1/0 df=58 of=0 ql=634 qs=NRW. kt=0/W/1 ktl=58c b=10 ci=191037 co=0 ca=0 + 2 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=1081/1/0 df=175 of=0 ql=74 qs=N.W. kt=0/W/2 ktl=da94 b=10 ci=75991 co=0 ca=0 + 3 c=20942 g=20943 pq=1 pgp=20942 qp=1 dt=1846/0/0 df=404 of=0 ql=0 qs=.... kt=0/W/3 ktl=d1cd b=10 ci=72261 co=0 ca=0 + 4 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=369/1/0 df=83 of=0 ql=48 qs=N.W. kt=0/W/4 ktl=e0e7 b=10 ci=128365 co=0 ca=0 + 5 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=381/1/0 df=64 of=0 ql=169 qs=NRW. kt=0/W/5 ktl=fb2f b=10 ci=164360 co=0 ca=0 + 6 c=20972 g=20973 pq=1 pgp=20973 qp=0 dt=1037/1/0 df=183 of=0 ql=62 qs=N.W. kt=0/W/6 ktl=d2ad b=10 ci=65663 co=0 ca=0 + 7 c=20897 g=20897 pq=1 pgp=20896 qp=0 dt=1572/0/0 df=382 of=0 ql=0 qs=.... kt=0/W/7 ktl=cf15 b=10 ci=75006 co=0 ca=0 rcu_bh: - 0 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=545/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/0 ktl=ebc3 b=10 ci=0 co=0 ca=0 - 1 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=967/1/0 df=3 of=0 ri=1 ql=0 qs=.... kt=0/W/1 ktl=58c b=10 ci=151 co=0 ca=0 - 2 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=1081/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/2 ktl=da94 b=10 ci=0 co=0 ca=0 - 3 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=1846/0/0 df=8 of=0 ri=1 ql=0 qs=.... kt=0/W/3 ktl=d1cd b=10 ci=0 co=0 ca=0 - 4 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=369/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/4 ktl=e0e7 b=10 ci=0 co=0 ca=0 - 5 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=381/1/0 df=4 of=0 ri=1 ql=0 qs=.... kt=0/W/5 ktl=fb2f b=10 ci=0 co=0 ca=0 - 6 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=1037/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/6 ktl=d2ad b=10 ci=0 co=0 ca=0 - 7 c=1474 g=1474 pq=1 pgp=1473 qp=0 dt=1572/0/0 df=8 of=0 ri=1 ql=0 qs=.... kt=0/W/7 ktl=cf15 b=10 ci=0 co=0 ca=0 + 0 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=545/1/0 df=6 of=0 ql=0 qs=.... kt=0/W/0 ktl=ebc3 b=10 ci=0 co=0 ca=0 + 1 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=967/1/0 df=3 of=0 ql=0 qs=.... kt=0/W/1 ktl=58c b=10 ci=151 co=0 ca=0 + 2 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=1081/1/0 df=6 of=0 ql=0 qs=.... kt=0/W/2 ktl=da94 b=10 ci=0 co=0 ca=0 + 3 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=1846/0/0 df=8 of=0 ql=0 qs=.... kt=0/W/3 ktl=d1cd b=10 ci=0 co=0 ca=0 + 4 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=369/1/0 df=6 of=0 ql=0 qs=.... kt=0/W/4 ktl=e0e7 b=10 ci=0 co=0 ca=0 + 5 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=381/1/0 df=4 of=0 ql=0 qs=.... kt=0/W/5 ktl=fb2f b=10 ci=0 co=0 ca=0 + 6 c=1480 g=1480 pq=1 pgp=1480 qp=0 dt=1037/1/0 df=6 of=0 ql=0 qs=.... kt=0/W/6 ktl=d2ad b=10 ci=0 co=0 ca=0 + 7 c=1474 g=1474 pq=1 pgp=1473 qp=0 dt=1572/0/0 df=8 of=0 ql=0 qs=.... kt=0/W/7 ktl=cf15 b=10 ci=0 co=0 ca=0 The first section lists the rcu_data structures for rcu_sched, the second for rcu_bh. Note that CONFIG_TREE_PREEMPT_RCU kernels will have an @@ -119,10 +119,6 @@ o "of" is the number of times that some other CPU has forced a CPU is offline when it is really alive and kicking) is a fatal error, so it makes sense to err conservatively. -o "ri" is the number of times that RCU has seen fit to send a - reschedule IPI to this CPU in order to get it to report a - quiescent state. - o "ql" is the number of RCU callbacks currently residing on this CPU. This is the total number of callbacks, regardless of what state they are in (new, waiting for grace period to diff --git a/Documentation/hwmon/w83627ehf b/Documentation/hwmon/w83627ehf index 3f44dbdfda7..ceaf6f652b0 100644 --- a/Documentation/hwmon/w83627ehf +++ b/Documentation/hwmon/w83627ehf @@ -50,7 +50,7 @@ W83627DHG, W83627DHG-P, W83627UHG, W83667HG, W83667HG-B, W83667HG-I (NCT6775F), and NCT6776F super I/O chips. We will refer to them collectively as Winbond chips. -The chips implement 2 to 4 temperature sensors (9 for NCT6775F and NCT6776F), +The chips implement 3 to 4 temperature sensors (9 for NCT6775F and NCT6776F), 2 to 5 fan rotation speed sensors, 8 to 10 analog voltage sensors, one VID (except for 627UHG), alarms with beep warnings (control unimplemented), and some automatic fan regulation strategies (plus manual fan control mode). @@ -143,8 +143,13 @@ pwm[1-4]_min_output - minimum fan speed (range 1 - 255), when the temperature pwm[1-4]_stop_time - how many milliseconds [ms] must elapse to switch corresponding fan off. (when the temperature was below defined range). +pwm[1-4]_start_output-minimum fan speed (range 1 - 255) when spinning up +pwm[1-4]_step_output- rate of fan speed change (1 - 255) +pwm[1-4]_stop_output- minimum fan speed (range 1 - 255) when spinning down +pwm[1-4]_max_output - maximum fan speed (range 1 - 255), when the temperature + is above defined range. -Note: last two functions are influenced by other control bits, not yet exported +Note: last six functions are influenced by other control bits, not yet exported by the driver, so a change might not have any effect. Implementation Details diff --git a/Documentation/hwmon/zl6100 b/Documentation/hwmon/zl6100 index 51f76a189fe..a4e8d90f59f 100644 --- a/Documentation/hwmon/zl6100 +++ b/Documentation/hwmon/zl6100 @@ -88,14 +88,12 @@ Module parameters delay ----- -Some Intersil/Zilker Labs DC-DC controllers require a minimum interval between -I2C bus accesses. According to Intersil, the minimum interval is 2 ms, though -1 ms appears to be sufficient and has not caused any problems in testing. -The problem is known to affect ZL6100, ZL2105, and ZL2008. It is known not to -affect ZL2004 and ZL6105. The driver automatically sets the interval to 1 ms -except for ZL2004 and ZL6105. To enable manual override, the driver provides a -writeable module parameter, 'delay', which can be used to set the interval to -a value between 0 and 65,535 microseconds. +Intersil/Zilker Labs DC-DC controllers require a minimum interval between I2C +bus accesses. According to Intersil, the minimum interval is 2 ms, though 1 ms +appears to be sufficient and has not caused any problems in testing. The problem +is known to affect all currently supported chips. For manual override, the +driver provides a writeable module parameter, 'delay', which can be used to set +the interval to a value between 0 and 65,535 microseconds. Sysfs entries diff --git a/Documentation/lockup-watchdogs.txt b/Documentation/lockup-watchdogs.txt new file mode 100644 index 00000000000..d2a36602ca8 --- /dev/null +++ b/Documentation/lockup-watchdogs.txt @@ -0,0 +1,63 @@ +=============================================================== +Softlockup detector and hardlockup detector (aka nmi_watchdog) +=============================================================== + +The Linux kernel can act as a watchdog to detect both soft and hard +lockups. + +A 'softlockup' is defined as a bug that causes the kernel to loop in +kernel mode for more than 20 seconds (see "Implementation" below for +details), without giving other tasks a chance to run. The current +stack trace is displayed upon detection and, by default, the system +will stay locked up. Alternatively, the kernel can be configured to +panic; a sysctl, "kernel.softlockup_panic", a kernel parameter, +"softlockup_panic" (see "Documentation/kernel-parameters.txt" for +details), and a compile option, "BOOTPARAM_HARDLOCKUP_PANIC", are +provided for this. + +A 'hardlockup' is defined as a bug that causes the CPU to loop in +kernel mode for more than 10 seconds (see "Implementation" below for +details), without letting other interrupts have a chance to run. +Similarly to the softlockup case, the current stack trace is displayed +upon detection and the system will stay locked up unless the default +behavior is changed, which can be done through a compile time knob, +"BOOTPARAM_HARDLOCKUP_PANIC", and a kernel parameter, "nmi_watchdog" +(see "Documentation/kernel-parameters.txt" for details). + +The panic option can be used in combination with panic_timeout (this +timeout is set through the confusingly named "kernel.panic" sysctl), +to cause the system to reboot automatically after a specified amount +of time. + +=== Implementation === + +The soft and hard lockup detectors are built on top of the hrtimer and +perf subsystems, respectively. A direct consequence of this is that, +in principle, they should work in any architecture where these +subsystems are present. + +A periodic hrtimer runs to generate interrupts and kick the watchdog +task. An NMI perf event is generated every "watchdog_thresh" +(compile-time initialized to 10 and configurable through sysctl of the +same name) seconds to check for hardlockups. If any CPU in the system +does not receive any hrtimer interrupt during that time the +'hardlockup detector' (the handler for the NMI perf event) will +generate a kernel warning or call panic, depending on the +configuration. + +The watchdog task is a high priority kernel thread that updates a +timestamp every time it is scheduled. If that timestamp is not updated +for 2*watchdog_thresh seconds (the softlockup threshold) the +'softlockup detector' (coded inside the hrtimer callback function) +will dump useful debug information to the system log, after which it +will call panic if it was instructed to do so or resume execution of +other kernel code. + +The period of the hrtimer is 2*watchdog_thresh/5, which means it has +two or three chances to generate an interrupt before the hardlockup +detector kicks in. + +As explained above, a kernel knob is provided that allows +administrators to configure the period of the hrtimer and the perf +event. The right value for a particular environment is a trade-off +between fast response to lockups and detection overhead. diff --git a/Documentation/nmi_watchdog.txt b/Documentation/nmi_watchdog.txt deleted file mode 100644 index bf9f80a9828..00000000000 --- a/Documentation/nmi_watchdog.txt +++ /dev/null @@ -1,83 +0,0 @@ - -[NMI watchdog is available for x86 and x86-64 architectures] - -Is your system locking up unpredictably? No keyboard activity, just -a frustrating complete hard lockup? Do you want to help us debugging -such lockups? If all yes then this document is definitely for you. - -On many x86/x86-64 type hardware there is a feature that enables -us to generate 'watchdog NMI interrupts'. (NMI: Non Maskable Interrupt -which get executed even if the system is otherwise locked up hard). -This can be used to debug hard kernel lockups. By executing periodic -NMI interrupts, the kernel can monitor whether any CPU has locked up, -and print out debugging messages if so. - -In order to use the NMI watchdog, you need to have APIC support in your -kernel. For SMP kernels, APIC support gets compiled in automatically. For -UP, enable either CONFIG_X86_UP_APIC (Processor type and features -> Local -APIC support on uniprocessors) or CONFIG_X86_UP_IOAPIC (Processor type and -features -> IO-APIC support on uniprocessors) in your kernel config. -CONFIG_X86_UP_APIC is for uniprocessor machines without an IO-APIC. -CONFIG_X86_UP_IOAPIC is for uniprocessor with an IO-APIC. [Note: certain -kernel debugging options, such as Kernel Stack Meter or Kernel Tracer, -may implicitly disable the NMI watchdog.] - -For x86-64, the needed APIC is always compiled in. - -Using local APIC (nmi_watchdog=2) needs the first performance register, so -you can't use it for other purposes (such as high precision performance -profiling.) However, at least oprofile and the perfctr driver disable the -local APIC NMI watchdog automatically. - -To actually enable the NMI watchdog, use the 'nmi_watchdog=N' boot -parameter. Eg. the relevant lilo.conf entry: - - append="nmi_watchdog=1" - -For SMP machines and UP machines with an IO-APIC use nmi_watchdog=1. -For UP machines without an IO-APIC use nmi_watchdog=2, this only works -for some processor types. If in doubt, boot with nmi_watchdog=1 and -check the NMI count in /proc/interrupts; if the count is zero then -reboot with nmi_watchdog=2 and check the NMI count. If it is still -zero then log a problem, you probably have a processor that needs to be -added to the nmi code. - -A 'lockup' is the following scenario: if any CPU in the system does not -execute the period local timer interrupt for more than 5 seconds, then -the NMI handler generates an oops and kills the process. This -'controlled crash' (and the resulting kernel messages) can be used to -debug the lockup. Thus whenever the lockup happens, wait 5 seconds and -the oops will show up automatically. If the kernel produces no messages -then the system has crashed so hard (eg. hardware-wise) that either it -cannot even accept NMI interrupts, or the crash has made the kernel -unable to print messages. - -Be aware that when using local APIC, the frequency of NMI interrupts -it generates, depends on the system load. The local APIC NMI watchdog, -lacking a better source, uses the "cycles unhalted" event. As you may -guess it doesn't tick when the CPU is in the halted state (which happens -when the system is idle), but if your system locks up on anything but the -"hlt" processor instruction, the watchdog will trigger very soon as the -"cycles unhalted" event will happen every clock tick. If it locks up on -"hlt", then you are out of luck -- the event will not happen at all and the -watchdog won't trigger. This is a shortcoming of the local APIC watchdog --- unfortunately there is no "clock ticks" event that would work all the -time. The I/O APIC watchdog is driven externally and has no such shortcoming. -But its NMI frequency is much higher, resulting in a more significant hit -to the overall system performance. - -On x86 nmi_watchdog is disabled by default so you have to enable it with -a boot time parameter. - -It's possible to disable the NMI watchdog in run-time by writing "0" to -/proc/sys/kernel/nmi_watchdog. Writing "1" to the same file will re-enable -the NMI watchdog. Notice that you still need to use "nmi_watchdog=" parameter -at boot time. - -NOTE: In kernels prior to 2.4.2-ac18 the NMI-oopser is enabled unconditionally -on x86 SMP boxes. - -[ feel free to send bug reports, suggestions and patches to - Ingo Molnar <mingo@redhat.com> or the Linux SMP mailing - list at <linux-smp@vger.kernel.org> ] - diff --git a/Documentation/static-keys.txt b/Documentation/static-keys.txt new file mode 100644 index 00000000000..d93f3c00f24 --- /dev/null +++ b/Documentation/static-keys.txt @@ -0,0 +1,286 @@ + Static Keys + ----------- + +By: Jason Baron <jbaron@redhat.com> + +0) Abstract + +Static keys allows the inclusion of seldom used features in +performance-sensitive fast-path kernel code, via a GCC feature and a code +patching technique. A quick example: + + struct static_key key = STATIC_KEY_INIT_FALSE; + + ... + + if (static_key_false(&key)) + do unlikely code + else + do likely code + + ... + static_key_slow_inc(); + ... + static_key_slow_inc(); + ... + +The static_key_false() branch will be generated into the code with as little +impact to the likely code path as possible. + + +1) Motivation + + +Currently, tracepoints are implemented using a conditional branch. The +conditional check requires checking a global variable for each tracepoint. +Although the overhead of this check is small, it increases when the memory +cache comes under pressure (memory cache lines for these global variables may +be shared with other memory accesses). As we increase the number of tracepoints +in the kernel this overhead may become more of an issue. In addition, +tracepoints are often dormant (disabled) and provide no direct kernel +functionality. Thus, it is highly desirable to reduce their impact as much as +possible. Although tracepoints are the original motivation for this work, other +kernel code paths should be able to make use of the static keys facility. + + +2) Solution + + +gcc (v4.5) adds a new 'asm goto' statement that allows branching to a label: + +http://gcc.gnu.org/ml/gcc-patches/2009-07/msg01556.html + +Using the 'asm goto', we can create branches that are either taken or not taken +by default, without the need to check memory. Then, at run-time, we can patch +the branch site to change the branch direction. + +For example, if we have a simple branch that is disabled by default: + + if (static_key_false(&key)) + printk("I am the true branch\n"); + +Thus, by default the 'printk' will not be emitted. And the code generated will +consist of a single atomic 'no-op' instruction (5 bytes on x86), in the +straight-line code path. When the branch is 'flipped', we will patch the +'no-op' in the straight-line codepath with a 'jump' instruction to the +out-of-line true branch. Thus, changing branch direction is expensive but +branch selection is basically 'free'. That is the basic tradeoff of this +optimization. + +This lowlevel patching mechanism is called 'jump label patching', and it gives +the basis for the static keys facility. + +3) Static key label API, usage and examples: + + +In order to make use of this optimization you must first define a key: + + struct static_key key; + +Which is initialized as: + + struct static_key key = STATIC_KEY_INIT_TRUE; + +or: + + struct static_key key = STATIC_KEY_INIT_FALSE; + +If the key is not initialized, it is default false. The 'struct static_key', +must be a 'global'. That is, it can't be allocated on the stack or dynamically +allocated at run-time. + +The key is then used in code as: + + if (static_key_false(&key)) + do unlikely code + else + do likely code + +Or: + + if (static_key_true(&key)) + do likely code + else + do unlikely code + +A key that is initialized via 'STATIC_KEY_INIT_FALSE', must be used in a +'static_key_false()' construct. Likewise, a key initialized via +'STATIC_KEY_INIT_TRUE' must be used in a 'static_key_true()' construct. A +single key can be used in many branches, but all the branches must match the +way that the key has been initialized. + +The branch(es) can then be switched via: + + static_key_slow_inc(&key); + ... + static_key_slow_dec(&key); + +Thus, 'static_key_slow_inc()' means 'make the branch true', and +'static_key_slow_dec()' means 'make the the branch false' with appropriate +reference counting. For example, if the key is initialized true, a +static_key_slow_dec(), will switch the branch to false. And a subsequent +static_key_slow_inc(), will change the branch back to true. Likewise, if the +key is initialized false, a 'static_key_slow_inc()', will change the branch to +true. And then a 'static_key_slow_dec()', will again make the branch false. + +An example usage in the kernel is the implementation of tracepoints: + + static inline void trace_##name(proto) \ + { \ + if (static_key_false(&__tracepoint_##name.key)) \ + __DO_TRACE(&__tracepoint_##name, \ + TP_PROTO(data_proto), \ + TP_ARGS(data_args), \ + TP_CONDITION(cond)); \ + } + +Tracepoints are disabled by default, and can be placed in performance critical +pieces of the kernel. Thus, by using a static key, the tracepoints can have +absolutely minimal impact when not in use. + + +4) Architecture level code patching interface, 'jump labels' + + +There are a few functions and macros that architectures must implement in order +to take advantage of this optimization. If there is no architecture support, we +simply fall back to a traditional, load, test, and jump sequence. + +* select HAVE_ARCH_JUMP_LABEL, see: arch/x86/Kconfig + +* #define JUMP_LABEL_NOP_SIZE, see: arch/x86/include/asm/jump_label.h + +* __always_inline bool arch_static_branch(struct static_key *key), see: + arch/x86/include/asm/jump_label.h + +* void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type type), + see: arch/x86/kernel/jump_label.c + +* __init_or_module void arch_jump_label_transform_static(struct jump_entry *entry, enum jump_label_type type), + see: arch/x86/kernel/jump_label.c + + +* struct jump_entry, see: arch/x86/include/asm/jump_label.h + + +5) Static keys / jump label analysis, results (x86_64): + + +As an example, let's add the following branch to 'getppid()', such that the +system call now looks like: + +SYSCALL_DEFINE0(getppid) +{ + int pid; + ++ if (static_key_false(&key)) ++ printk("I am the true branch\n"); + + rcu_read_lock(); + pid = task_tgid_vnr(rcu_dereference(current->real_parent)); + rcu_read_unlock(); + + return pid; +} + +The resulting instructions with jump labels generated by GCC is: + +ffffffff81044290 <sys_getppid>: +ffffffff81044290: 55 push %rbp +ffffffff81044291: 48 89 e5 mov %rsp,%rbp +ffffffff81044294: e9 00 00 00 00 jmpq ffffffff81044299 <sys_getppid+0x9> +ffffffff81044299: 65 48 8b 04 25 c0 b6 mov %gs:0xb6c0,%rax +ffffffff810442a0: 00 00 +ffffffff810442a2: 48 8b 80 80 02 00 00 mov 0x280(%rax),%rax +ffffffff810442a9: 48 8b 80 b0 02 00 00 mov 0x2b0(%rax),%rax +ffffffff810442b0: 48 8b b8 e8 02 00 00 mov 0x2e8(%rax),%rdi +ffffffff810442b7: e8 f4 d9 00 00 callq ffffffff81051cb0 <pid_vnr> +ffffffff810442bc: 5d pop %rbp +ffffffff810442bd: 48 98 cltq +ffffffff810442bf: c3 retq +ffffffff810442c0: 48 c7 c7 e3 54 98 81 mov $0xffffffff819854e3,%rdi +ffffffff810442c7: 31 c0 xor %eax,%eax +ffffffff810442c9: e8 71 13 6d 00 callq ffffffff8171563f <printk> +ffffffff810442ce: eb c9 jmp ffffffff81044299 <sys_getppid+0x9> + +Without the jump label optimization it looks like: + +ffffffff810441f0 <sys_getppid>: +ffffffff810441f0: 8b 05 8a 52 d8 00 mov 0xd8528a(%rip),%eax # ffffffff81dc9480 <key> +ffffffff810441f6: 55 push %rbp +ffffffff810441f7: 48 89 e5 mov %rsp,%rbp +ffffffff810441fa: 85 c0 test %eax,%eax +ffffffff810441fc: 75 27 jne ffffffff81044225 <sys_getppid+0x35> +ffffffff810441fe: 65 48 8b 04 25 c0 b6 mov %gs:0xb6c0,%rax +ffffffff81044205: 00 00 +ffffffff81044207: 48 8b 80 80 02 00 00 mov 0x280(%rax),%rax +ffffffff8104420e: 48 8b 80 b0 02 00 00 mov 0x2b0(%rax),%rax +ffffffff81044215: 48 8b b8 e8 02 00 00 mov 0x2e8(%rax),%rdi +ffffffff8104421c: e8 2f da 00 00 callq ffffffff81051c50 <pid_vnr> +ffffffff81044221: 5d pop %rbp +ffffffff81044222: 48 98 cltq +ffffffff81044224: c3 retq +ffffffff81044225: 48 c7 c7 13 53 98 81 mov $0xffffffff81985313,%rdi +ffffffff8104422c: 31 c0 xor %eax,%eax +ffffffff8104422e: e8 60 0f 6d 00 callq ffffffff81715193 <printk> +ffffffff81044233: eb c9 jmp ffffffff810441fe <sys_getppid+0xe> +ffffffff81044235: 66 66 2e 0f 1f 84 00 data32 nopw %cs:0x0(%rax,%rax,1) +ffffffff8104423c: 00 00 00 00 + +Thus, the disable jump label case adds a 'mov', 'test' and 'jne' instruction +vs. the jump label case just has a 'no-op' or 'jmp 0'. (The jmp 0, is patched +to a 5 byte atomic no-op instruction at boot-time.) Thus, the disabled jump +label case adds: + +6 (mov) + 2 (test) + 2 (jne) = 10 - 5 (5 byte jump 0) = 5 addition bytes. + +If we then include the padding bytes, the jump label code saves, 16 total bytes +of instruction memory for this small fucntion. In this case the non-jump label +function is 80 bytes long. Thus, we have have saved 20% of the instruction +footprint. We can in fact improve this even further, since the 5-byte no-op +really can be a 2-byte no-op since we can reach the branch with a 2-byte jmp. +However, we have not yet implemented optimal no-op sizes (they are currently +hard-coded). + +Since there are a number of static key API uses in the scheduler paths, +'pipe-test' (also known as 'perf bench sched pipe') can be used to show the +performance improvement. Testing done on 3.3.0-rc2: + +jump label disabled: + + Performance counter stats for 'bash -c /tmp/pipe-test' (50 runs): + + 855.700314 task-clock # 0.534 CPUs utilized ( +- 0.11% ) + 200,003 context-switches # 0.234 M/sec ( +- 0.00% ) + 0 CPU-migrations # 0.000 M/sec ( +- 39.58% ) + 487 page-faults # 0.001 M/sec ( +- 0.02% ) + 1,474,374,262 cycles # 1.723 GHz ( +- 0.17% ) + <not supported> stalled-cycles-frontend + <not supported> stalled-cycles-backend + 1,178,049,567 instructions # 0.80 insns per cycle ( +- 0.06% ) + 208,368,926 branches # 243.507 M/sec ( +- 0.06% ) + 5,569,188 branch-misses # 2.67% of all branches ( +- 0.54% ) + + 1.601607384 seconds time elapsed ( +- 0.07% ) + +jump label enabled: + + Performance counter stats for 'bash -c /tmp/pipe-test' (50 runs): + + 841.043185 task-clock # 0.533 CPUs utilized ( +- 0.12% ) + 200,004 context-switches # 0.238 M/sec ( +- 0.00% ) + 0 CPU-migrations # 0.000 M/sec ( +- 40.87% ) + 487 page-faults # 0.001 M/sec ( +- 0.05% ) + 1,432,559,428 cycles # 1.703 GHz ( +- 0.18% ) + <not supported> stalled-cycles-frontend + <not supported> stalled-cycles-backend + 1,175,363,994 instructions # 0.82 insns per cycle ( +- 0.04% ) + 206,859,359 branches # 245.956 M/sec ( +- 0.04% ) + 4,884,119 branch-misses # 2.36% of all branches ( +- 0.85% ) + + 1.579384366 seconds time elapsed + +The percentage of saved branches is .7%, and we've saved 12% on +'branch-misses'. This is where we would expect to get the most savings, since +this optimization is about reducing the number of branches. In addition, we've +saved .2% on instructions, and 2.8% on cycles and 1.4% on elapsed time. diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt index 1ebc24cf9a5..6f51fed45f2 100644 --- a/Documentation/trace/ftrace.txt +++ b/Documentation/trace/ftrace.txt @@ -226,6 +226,13 @@ Here is the list of current tracers that may be configured. Traces and records the max latency that it takes for the highest priority task to get scheduled after it has been woken up. + Traces all tasks as an average developer would expect. + + "wakeup_rt" + + Traces and records the max latency that it takes for just + RT tasks (as the current "wakeup" does). This is useful + for those interested in wake up timings of RT tasks. "hw-branch-tracer" |