123 строки
5.1 KiB
ReStructuredText
123 строки
5.1 KiB
ReStructuredText
============================
|
|
Kernel NFS Server Statistics
|
|
============================
|
|
|
|
:Authors: Greg Banks <gnb@sgi.com> - 26 Mar 2009
|
|
|
|
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 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
|
|
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.
|
|
|
|
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.
|