kern/131360: [nfs] poor scaling behavior of the NFS server under load

[Martin Birgmeier]

The following reply was made to PR kern/131360; it has been noted by GNATS.

From: Martin Birgmeier <martin at email.aon.at>
To: bug-followup at FreeBSD.org
Cc:  
Subject: Re: kern/131360: [nfs] poor scaling behavior of the NFS server under load
Date: Sun, 8 Feb 2009 09:12:46 +0100 (CET)

 Another top snapshot on the server, scenario is the following:
   - make -j4 buildworld running on the client, currently in
     "===> kerberos5/lib/libkadm5srv (all)"
   - on the server, in addition to serving NFS, also running
     a 'svn log' command, where the repository is also served
     by the server via http (httpd, subversion repo, and svn log
     all running on the server, displaying in an XTerm running
     on the client).
 
 If I do the 'svn log' without NFS load from the client (buildworld
 stopped), there is nearly instantaneous output. If I do it with a
 running buildworld on the client, I get the a top output similar
 to the one below (actually, it is very hard to capture the "worst"
 moments, as the server is so unresponsive - in fact the load was
 something like 25, and each of the 8 nfsds consumed about 10% of
 CPU).
 
 last pid:  2527;  load averages: 14.71, 10.36,  6.13    up 0+01:04:43  08:21:08
 111 processes: 9 running, 102 sleeping
 CPU:  1.4% user,  0.0% nice, 90.5% system,  8.1% interrupt,  0.0% idle
 Mem: 135M Active, 745M Inact, 119M Wired, 1012K Cache, 112M Buf, 248M Free
 Swap: 2048M Total, 2048M Free
 
   PID USERNAME    THR PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND
   971 root          1   4    0  3128K   944K -       13:45 40.28% nfsd
   972 root          1   4    0  3128K   944K -        2:19 15.09% nfsd
   973 root          1   4    0  3128K   944K -        1:31 10.16% nfsd
   974 root          1   4    0  3128K   944K -        1:03  6.05% nfsd
   975 root          1   4    0  3128K   944K -        0:49  4.59% nfsd
   977 root          1   4    0  3128K   944K -        0:41  3.56% nfsd
   978 root          1   4    0  3128K   944K -        0:35  2.64% nfsd
   976 root          1   4    0  3128K   944K -        0:31  1.81% nfsd
  2527 root          1  96    0  3164K   992K RUN      0:00  1.54% rsh
  1471 root          1  81  -15  5032K  2716K select   0:05  0.05% ppp
   919 root          1  96    0  3128K  3148K select   2:16  0.00% amd
  1539 root          1  96    0  6508K  4964K RUN      0:10  0.00% xterm
  1140 squid         1   4    0 12000K 10152K sbwait   0:05  0.00% perl5.8.9
  1130 squid         1  96    0 15660K 10820K RUN      0:05  0.00% squid
  1141 squid         1   4    0 12000K 10148K sbwait   0:04  0.00% perl5.8.9
  1142 squid         1   4    0 12000K 10148K sbwait   0:04  0.00% perl5.8.9
  1143 squid         1   4    0 12000K 10104K sbwait   0:03  0.00% perl5.8.9