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SubjectRe: [2.6.30.1] Significant latency playing video file from NFS4 share
Date
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:

   op/s         rpc bklog
   0.65            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.406         101.661         250.613        0 (0.0%)         1211.745        1222.640
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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:

   op/s         rpc bklog
   0.25            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.100           0.426           4.262        0 (0.0%)           6.000           6.000
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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:

   op/s         rpc bklog
   0.80            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.750         192.196         256.262        0 (0.0%)         1998.933        1999.200
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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:

   op/s         rpc bklog
   0.00            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (0.0%)           0.000           0.000
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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:

   op/s         rpc bklog
   0.85            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.750         192.196         256.262        0 (0.0%)         1927.467        1927.467
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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:

   op/s         rpc bklog
   0.00            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (0.0%)           0.000           0.000
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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:

   op/s         rpc bklog
   0.85            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.750         192.196         256.262        0 (0.0%)         1930.933        1931.467
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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:

   op/s         rpc bklog
   0.15            0.00
read:             ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.100           0.426           4.262        0 (0.0%)           6.000           6.000
write:            ops/s            kB/s           kB/op         retrans         avg RTT (ms)    avg exe (ms)
                  0.000           0.000           0.000        0 (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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