NFS Client Performance Question

[Chris Penney <cpenney@gmail.com>]

I have a large smp SGI Itanium box box running a 2.4.21 kernel and I'm
getting fairly bad NFS performance, esp. when doing random writes to
an unloaded NFS server.  The box is rather busy doing computation and
a lot of i/o to /tmp; however, there is little network i/o (<100
KB/s).  I use iozone with the following options to test "-c -e -i 2 -w
-s 16m" and use an unloaded Sun NFS server (same performance results
with Linux NFS servers, but they are all under load so I test with the
Sun).  I only get ~2.5MB/s using the above test.  I found an Intel box
still running a 2.4.20 kernel and it gets 15MB/s.  On a 2.6 kernel box
the rate jumps to 46MB/s (nice work).

I did some sniffing on the Sun and noticed that the problem Itanium
system was not doing async writes (snips are from the start of the
write test):

[snip]
redhat -> server NFS C WRITE3 FH=3D40E5 at 1478656 for 4096 (ASYNC)
server -> redhat NFS R WRITE3 OK 4096 (ASYNC)
redhat -> server NFS C WRITE3 FH=3D40E5 at 1179648 for 4096 (ASYNC)
[snip]
itanium -> server NFS C WRITE3 FH=3D40E5 at 4239360 for 4096 (FSYNC)
server -> server NFS R WRITE3 OK 4096 (FSYNC)
server -> server NFS C WRITE3 FH=3D40E5 at 15101952 for 4096 (FSYNC)
[snip]

The client mount options are:
   rw,nosuid,bg,hard,intr,nfsvers=3D3,tcp,rsize=3D32768,wsize=3D32768

So my question: Is the Itanium system not doing async nfs i/o because
nfract_sync has been exceeded due to local i/o to /tmp or is it
something else?  Is there anything I can do to improve NFS performance
on this box?

   Chris


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