Re: 2.4.21 NFSv3 performance graph

[Jeff Blaine <jblaine@mitre.org>]

Trond Myklebust wrote:
> fr den 14.01.2005 Klokka 14:00 (-0500) skreiv Jeff Blaine:
>=20
>>Can anyone tell me what is happening in the graph at the URL
>>below?  I can replicate it on any Linux box running 2.4.21
>>and changing rsize/wsize doesn't affect it at all.  This
>>was captured from a 2.6GHz P4 client machine.  Same thing
>>is visible with a Dual 3GHz Xeon box with 4GB memory as a
>>client.  A Solaris 9 client does not display this "falling
>>on face" behavior.
>>
>>http://www.kickflop.net/temp/sol9-server-linux2421-client-gigE-ag930m_1=
0533_image001.gif
>=20
> Firstly, you should always use the '-c' flag when measuring NFS client
> performance. Otherwise, you are basically just measuring the speed with
> which your machine can write to the local page cache (which may indeed
> explain your "knee" at 1MB here - that would be where the client starts
> to force a flush to disk).

Firstly,

Iozone manual:

     "If you use a file size that is larger than the amount of
      memory in the client then the =91c=92 flag is not needed."

I used a file size that is larger than the amount of memory in
the client.

> Secondly, have you actually read the NFS FAQ and NFS HOWTO entries on
> how to tune for performance? Particularly the entries on TCP vs. UDP,
> and how Solaris clients default to the former.

Secondly,

Yes, I have *actually* read the NFS FAQ and NFS HOWTO entries
on how to tune for performance.

It was a pretty simple question.  I don't know what all the
attitude is about.  Do you have an answer you can share with
me or not?

Anyone else?



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