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author | J. Bruce Fields <bfields@citi.umich.edu> | 2009-11-06 13:59:43 -0500 |
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committer | J. Bruce Fields <bfields@citi.umich.edu> | 2009-11-06 14:01:02 -0500 |
commit | ea4878a24d7e6a467d369b962bab95bd6a12cbe0 (patch) | |
tree | 4f937b8dfa658b16779ae2267d450b53fb035fe7 /Documentation/filesystems/knfsd-stats.txt | |
parent | 8c10cbdb4af642d9a2efb45ea89251aaab905360 (diff) |
nfs: move more to Documentation/filesystems/nfs
Oops: I missed two files in the first commit that created this
directory.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Diffstat (limited to 'Documentation/filesystems/knfsd-stats.txt')
-rw-r--r-- | Documentation/filesystems/knfsd-stats.txt | 159 |
1 files changed, 0 insertions, 159 deletions
diff --git a/Documentation/filesystems/knfsd-stats.txt b/Documentation/filesystems/knfsd-stats.txt deleted file mode 100644 index 64ced5149d3..00000000000 --- a/Documentation/filesystems/knfsd-stats.txt +++ /dev/null @@ -1,159 +0,0 @@ - -Kernel NFS Server Statistics -============================ - -This document describes the format and semantics of the statistics -which the kernel NFS server makes available to userspace. These -statistics are available in several text form pseudo files, each of -which is described separately below. - -In most cases you don't need to know these formats, as the nfsstat(8) -program from the nfs-utils distribution provides a helpful command-line -interface for extracting and printing them. - -All the files described here are formatted as a sequence of text lines, -separated by newline '\n' characters. Lines beginning with a hash -'#' character are comments intended for humans and should be ignored -by parsing routines. All other lines contain a sequence of fields -separated by whitespace. - -/proc/fs/nfsd/pool_stats ------------------------- - -This file is available in kernels from 2.6.30 onwards, if the -/proc/fs/nfsd filesystem is mounted (it almost always should be). - -The first line is a comment which describes the fields present in -all the other lines. The other lines present the following data as -a sequence of unsigned decimal numeric fields. One line is shown -for each NFS thread pool. - -All counters are 64 bits wide and wrap naturally. There is no way -to zero these counters, instead applications should do their own -rate conversion. - -pool - The id number of the NFS thread pool to which this line applies. - This number does not change. - - Thread pool ids are a contiguous set of small integers starting - at zero. The maximum value depends on the thread pool mode, but - currently cannot be larger than the number of CPUs in the system. - Note that in the default case there will be a single thread pool - which contains all the nfsd threads and all the CPUs in the system, - and thus this file will have a single line with a pool id of "0". - -packets-arrived - Counts how many NFS packets have arrived. More precisely, this - is the number of times that the network stack has notified the - sunrpc server layer that new data may be available on a transport - (e.g. an NFS or UDP socket or an NFS/RDMA endpoint). - - Depending on the NFS workload patterns and various network stack - effects (such as Large Receive Offload) which can combine packets - on the wire, this may be either more or less than the number - of NFS calls received (which statistic is available elsewhere). - However this is a more accurate and less workload-dependent measure - of how much CPU load is being placed on the sunrpc server layer - due to NFS network traffic. - -sockets-enqueued - Counts how many times an NFS transport is enqueued to wait for - an nfsd thread to service it, i.e. no nfsd thread was considered - available. - - The circumstance this statistic tracks indicates that there was NFS - network-facing work to be done but it couldn't be done immediately, - thus introducing a small delay in servicing NFS calls. The ideal - rate of change for this counter is zero; significantly non-zero - values may indicate a performance limitation. - - This can happen either because there are too few nfsd threads in the - thread pool for the NFS workload (the workload is thread-limited), - or because the NFS workload needs more CPU time than is available in - the thread pool (the workload is CPU-limited). In the former case, - configuring more nfsd threads will probably improve the performance - of the NFS workload. In the latter case, the sunrpc server layer is - already choosing not to wake idle nfsd threads because there are too - many nfsd threads which want to run but cannot, so configuring more - nfsd threads will make no difference whatsoever. The overloads-avoided - statistic (see below) can be used to distinguish these cases. - -threads-woken - Counts how many times an idle nfsd thread is woken to try to - receive some data from an NFS transport. - - This statistic tracks the circumstance where incoming - network-facing NFS work is being handled quickly, which is a good - thing. The ideal rate of change for this counter will be close - to but less than the rate of change of the packets-arrived counter. - -overloads-avoided - Counts how many times the sunrpc server layer chose not to wake an - nfsd thread, despite the presence of idle nfsd threads, because - too many nfsd threads had been recently woken but could not get - enough CPU time to actually run. - - This statistic counts a circumstance where the sunrpc layer - heuristically avoids overloading the CPU scheduler with too many - runnable nfsd threads. The ideal rate of change for this counter - is zero. Significant non-zero values indicate that the workload - is CPU limited. Usually this is associated with heavy CPU usage - on all the CPUs in the nfsd thread pool. - - If a sustained large overloads-avoided rate is detected on a pool, - the top(1) utility should be used to check for the following - pattern of CPU usage on all the CPUs associated with the given - nfsd thread pool. - - - %us ~= 0 (as you're *NOT* running applications on your NFS server) - - - %wa ~= 0 - - - %id ~= 0 - - - %sy + %hi + %si ~= 100 - - If this pattern is seen, configuring more nfsd threads will *not* - improve the performance of the workload. If this patten is not - seen, then something more subtle is wrong. - -threads-timedout - Counts how many times an nfsd thread triggered an idle timeout, - i.e. was not woken to handle any incoming network packets for - some time. - - This statistic counts a circumstance where there are more nfsd - threads configured than can be used by the NFS workload. This is - a clue that the number of nfsd threads can be reduced without - affecting performance. Unfortunately, it's only a clue and not - a strong indication, for a couple of reasons: - - - Currently the rate at which the counter is incremented is quite - slow; the idle timeout is 60 minutes. Unless the NFS workload - remains constant for hours at a time, this counter is unlikely - to be providing information that is still useful. - - - It is usually a wise policy to provide some slack, - i.e. configure a few more nfsds than are currently needed, - to allow for future spikes in load. - - -Note that incoming packets on NFS transports will be dealt with in -one of three ways. An nfsd thread can be woken (threads-woken counts -this case), or the transport can be enqueued for later attention -(sockets-enqueued counts this case), or the packet can be temporarily -deferred because the transport is currently being used by an nfsd -thread. This last case is not very interesting and is not explicitly -counted, but can be inferred from the other counters thus: - -packets-deferred = packets-arrived - ( sockets-enqueued + threads-woken ) - - -More ----- -Descriptions of the other statistics file should go here. - - -Greg Banks <gnb@sgi.com> -26 Mar 2009 |