diff options
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/cgroups/cpuacct.txt | 18 | ||||
-rw-r--r-- | Documentation/infiniband/ipoib.txt | 45 | ||||
-rw-r--r-- | Documentation/trace/ftrace.txt (renamed from Documentation/ftrace.txt) | 0 | ||||
-rw-r--r-- | Documentation/trace/kmemtrace.txt (renamed from Documentation/vm/kmemtrace.txt) | 0 | ||||
-rw-r--r-- | Documentation/trace/mmiotrace.txt (renamed from Documentation/tracers/mmiotrace.txt) | 0 | ||||
-rw-r--r-- | Documentation/trace/tracepoints.txt (renamed from Documentation/tracepoints.txt) | 0 |
6 files changed, 63 insertions, 0 deletions
diff --git a/Documentation/cgroups/cpuacct.txt b/Documentation/cgroups/cpuacct.txt index bb775fbe43d..8b930946c52 100644 --- a/Documentation/cgroups/cpuacct.txt +++ b/Documentation/cgroups/cpuacct.txt @@ -30,3 +30,21 @@ The above steps create a new group g1 and move the current shell process (bash) into it. CPU time consumed by this bash and its children can be obtained from g1/cpuacct.usage and the same is accumulated in /cgroups/cpuacct.usage also. + +cpuacct.stat file lists a few statistics which further divide the +CPU time obtained by the cgroup into user and system times. Currently +the following statistics are supported: + +user: Time spent by tasks of the cgroup in user mode. +system: Time spent by tasks of the cgroup in kernel mode. + +user and system are in USER_HZ unit. + +cpuacct controller uses percpu_counter interface to collect user and +system times. This has two side effects: + +- It is theoretically possible to see wrong values for user and system times. + This is because percpu_counter_read() on 32bit systems isn't safe + against concurrent writes. +- It is possible to see slightly outdated values for user and system times + due to the batch processing nature of percpu_counter. diff --git a/Documentation/infiniband/ipoib.txt b/Documentation/infiniband/ipoib.txt index 864ff328378..6d40f00b358 100644 --- a/Documentation/infiniband/ipoib.txt +++ b/Documentation/infiniband/ipoib.txt @@ -24,6 +24,49 @@ Partitions and P_Keys The P_Key for any interface is given by the "pkey" file, and the main interface for a subinterface is in "parent." +Datagram vs Connected modes + + The IPoIB driver supports two modes of operation: datagram and + connected. The mode is set and read through an interface's + /sys/class/net/<intf name>/mode file. + + In datagram mode, the IB UD (Unreliable Datagram) transport is used + and so the interface MTU has is equal to the IB L2 MTU minus the + IPoIB encapsulation header (4 bytes). For example, in a typical IB + fabric with a 2K MTU, the IPoIB MTU will be 2048 - 4 = 2044 bytes. + + In connected mode, the IB RC (Reliable Connected) transport is used. + Connected mode is to takes advantage of the connected nature of the + IB transport and allows an MTU up to the maximal IP packet size of + 64K, which reduces the number of IP packets needed for handling + large UDP datagrams, TCP segments, etc and increases the performance + for large messages. + + In connected mode, the interface's UD QP is still used for multicast + and communication with peers that don't support connected mode. In + this case, RX emulation of ICMP PMTU packets is used to cause the + networking stack to use the smaller UD MTU for these neighbours. + +Stateless offloads + + If the IB HW supports IPoIB stateless offloads, IPoIB advertises + TCP/IP checksum and/or Large Send (LSO) offloading capability to the + network stack. + + Large Receive (LRO) offloading is also implemented and may be turned + on/off using ethtool calls. Currently LRO is supported only for + checksum offload capable devices. + + Stateless offloads are supported only in datagram mode. + +Interrupt moderation + + If the underlying IB device supports CQ event moderation, one can + use ethtool to set interrupt mitigation parameters and thus reduce + the overhead incurred by handling interrupts. The main code path of + IPoIB doesn't use events for TX completion signaling so only RX + moderation is supported. + Debugging Information By compiling the IPoIB driver with CONFIG_INFINIBAND_IPOIB_DEBUG set @@ -55,3 +98,5 @@ References http://ietf.org/rfc/rfc4391.txt IP over InfiniBand (IPoIB) Architecture (RFC 4392) http://ietf.org/rfc/rfc4392.txt + IP over InfiniBand: Connected Mode (RFC 4755) + http://ietf.org/rfc/rfc4755.txt diff --git a/Documentation/ftrace.txt b/Documentation/trace/ftrace.txt index fd9a3e69381..fd9a3e69381 100644 --- a/Documentation/ftrace.txt +++ b/Documentation/trace/ftrace.txt diff --git a/Documentation/vm/kmemtrace.txt b/Documentation/trace/kmemtrace.txt index a956d9b7f94..a956d9b7f94 100644 --- a/Documentation/vm/kmemtrace.txt +++ b/Documentation/trace/kmemtrace.txt diff --git a/Documentation/tracers/mmiotrace.txt b/Documentation/trace/mmiotrace.txt index 5731c67abc5..5731c67abc5 100644 --- a/Documentation/tracers/mmiotrace.txt +++ b/Documentation/trace/mmiotrace.txt diff --git a/Documentation/tracepoints.txt b/Documentation/trace/tracepoints.txt index c0e1ceed75a..c0e1ceed75a 100644 --- a/Documentation/tracepoints.txt +++ b/Documentation/trace/tracepoints.txt |