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Documentation: remove overloads-avoided counter from knfsd-stats.txt

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The 'overloads-avoided' counter itself was removed several years ago by
commit 78c210e (Revert "knfsd: avoid overloading the CPU scheduler with
enormous load averages").

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Scott Mayhew 2015-04-29 10:38:26 -04:00 committed by J. Bruce Fields
parent fd89145460
commit 72faedae8b
1 changed files with 4 additions and 40 deletions
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44
Documentation/filesystems/nfs/knfsd-stats.txt
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@ -68,16 +68,10 @@ sockets-enqueued
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.
This can happen because there are too few nfsd threads in the thread
pool for the NFS workload (the workload is thread-limited), in which
case configuring more nfsd threads will probably improve the
performance of the NFS workload.
threads-woken
Counts how many times an idle nfsd thread is woken to try to
@ -88,36 +82,6 @@ threads-woken
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