Re: [2.6.30.1] Significant latency playing video file from NFS4 share
From: Frans Pop
Date: Tue Jul 21 2009 - 13:32:02 EST
Any suggestions based on the data below?
Is the problem maybe that the amount of data transferred each time is so
big that the network speed becomes a bottleneck and causes the latency?
I can reproduce the issue with both a 10MBit wired link and with a 54MBit
wireless link.
Is this a kernel bug or a configuration issue?
Thanks,
FJP
On Saturday 18 July 2009, Frans Pop wrote:
> Thanks for the quick response!
>
> On Saturday 18 July 2009, Trond Myklebust wrote:
> > Have you tried running nfs-iostat from the nfs-utils package to try
> > and figure out what the latency is on each READ request from the
> > client?
> >
> > You need to run something like
> >
> > nfs-iostat --page 20 10 /src/<mountpoint>
> >
> > while running the vlc app.
$ ../nfs-iostat.py --page 20 10 /srv/fjp/david
Note:
The mount point selection could be improved. I first had a trailing slash
after the mount point and that resulted in all mounts being included in the
output. Removing the slash helped.
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.65      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.406     101.661     250.613    Â0 (0.0%)     1211.745    Â1222.640
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
13 nfs_readpage() calls read 13 pages
1417 nfs_readpages() calls read 971428 pages (685.6 pages per call)
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
18760 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.25      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.100      0.426      4.262    Â0 (0.0%)      6.000      6.000
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
0 nfs_readpage() calls read 0 pages
2 nfs_readpages() calls read 2 pages (1.0 pages per call)
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
6 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.80      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.750     192.196     256.262    Â0 (0.0%)     1998.933    Â1999.200
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
0 nfs_readpage() calls read 0 pages
1 nfs_readpages() calls read 960 pages (960.0 pages per call)
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
6 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.00      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
0 nfs_readpage() calls read 0 pages
0 nfs_readpages() calls read 0 pages
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
6 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.85      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.750     192.196     256.262    Â0 (0.0%)     1927.467    Â1927.467
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
0 nfs_readpage() calls read 0 pages
1 nfs_readpages() calls read 960 pages (960.0 pages per call)
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
6 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.00      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
0 nfs_readpage() calls read 0 pages
0 nfs_readpages() calls read 0 pages
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
6 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.85      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.750     192.196     256.262    Â0 (0.0%)     1930.933    Â1931.467
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
0 nfs_readpage() calls read 0 pages
1 nfs_readpages() calls read 960 pages (960.0 pages per call)
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
5 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
elrond:/david mounted on /srv/fjp/david:
 Âop/s     rpc bklog
 Â0.15      Â0.00
read:       ops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.100      0.426      4.262    Â0 (0.0%)      6.000      6.000
write:      Âops/s      ÂkB/s      kB/op     retrans     avg RTT (ms)  Âavg exe (ms)
         0.000      0.000      0.000    Â0 (0.0%)      0.000      0.000
0 nfs_readpage() calls read 0 pages
2 nfs_readpages() calls read 2 pages (1.0 pages per call)
0 nfs_updatepage() calls
0 nfs_writepage() calls wrote 0 pages
6 nfs_writepages() calls wrote 0 pages (0.0 pages per call)
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