[nfsv4] Performance drop in iozone for reading large files

[Trond Myklebust]

On Tue, 2006-09-05 at 15:55 -0700, Bryce Harrington wrote:
> > Is the readahead algorithm working correctly? Could you please try
> > applying the following patch, and then check your syslog for warnings?
> 
> I just want to follow up on this one and make sure I understand it
> properly.
> 
> Dean says this is due to hitting the memory limit of server-side
> caching, which seems to explain it.  Our server has 1G memory, and when
> shrinking it to lower ram, the issue does occur earlier.

Do you see the same dropoff when running iozone locally on the server?
Personally, I would expect that the server itself should be doing
readahead too in order to mitigate these effects.

Cheers,
  Trond