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From: Andrew Theurer <habanero@us.ibm.com>
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To: Hirokazu Takahashi <taka@valinux.co.jp>
Subject: Re: [NFS] Re: [PATCH] zerocopy NFS for 2.5.36
Date: Tue, 22 Oct 2002 16:16:23 -0500
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On Saturday 19 October 2002 15:34, Hirokazu Takahashi wrote:
> Hello,
>
> > > Congestion avoidance mechanism of NFS clients might cause this
> > > situation.  I think the congestion window size is not enough
> > > for high end machines.  You can make the window be larger as a
> > > test.
> >
> > Is this a concern on the client only?  I can run a test with just one
> > client and see if I can saturate the 100Mbit adapter.  If I can, would we
> > need to make any adjustments then?  FYI, at 115 MB/sec total throughput,
> > that's only 2.875 MB/sec for each of the 40 clients.  For the TCP result
> > of 181 MB/sec, that's 4.525 MB/sec, IMO, both of which are comfortable
> > throughputs for a 100Mbit client.
>
> I think it's a client issue. NFS servers don't care about cogestion of UDP
> traffic and they will try to response to all NFS requests as fast as they
> can.
>
> You can try to increase the number of clients or the number of mount points
> for a test. It's easy to mount the same directory of the server on some
> directries of the client so that each of them can work simultaneously.
>    # mount -t nfs server:/foo   /baa1
>    # mount -t nfs server:/foo   /baa2
>    # mount -t nfs server:/foo   /baa3

I don't think it is a client congestion issue at this point.  I can run the 
test with just one client on UDP and achieve 11.2 MB/sec with just one mount 
point.  The client has 100 Mbit Ethernet, so should be the upper limit (or 
really close).  In the 40 client read test, I have only achieved 2.875 MB/sec 
per client.  That and the fact that there are never more than 2 nfsd threads 
in a run state at one time (for UDP only) leads me to believe there is still 
a scaling problem on the server for UDP.  I will continue to run the test and 
poke a prod around.  Hopefully something will jump out at me.  Thanks for all 
the input!

Andrew Theurer
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