linux-kernel - Re: Massive slowdown when re-querying large nfs dir

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Message-Id: <20071106221939.cfa79f9e.akpm@linux-foundation.org>
Date:	Tue, 6 Nov 2007 22:19:39 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Al Boldi <a1426z@...ab.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Neil Brown <neilb@...e.de>
Subject: Re: Massive slowdown when re-querying large nfs dir

> On Tue, 6 Nov 2007 14:28:11 +0300 Al Boldi <a1426z@...ab.com> wrote:
> Al Boldi wrote:
> > There is a massive (3-18x) slowdown when re-querying a large nfs dir (2k+
> > entries) using a simple ls -l.
> >
> > On 2.6.23 client and server running userland rpc.nfs.V2:
> > first  try: time -p ls -l <2k+ entry dir>  in ~2.5sec
> > more tries: time -p ls -l <2k+ entry dir>  in ~8sec
> >
> > first  try: time -p ls -l <5k+ entry dir>  in ~9sec
> > more tries: time -p ls -l <5k+ entry dir>  in ~180sec
> >
> > On 2.6.23 client and 2.4.31 server running userland rpc.nfs.V2:
> > first  try: time -p ls -l <2k+ entry dir>  in ~2.5sec
> > more tries: time -p ls -l <2k+ entry dir>  in ~7sec
> >
> > first  try: time -p ls -l <5k+ entry dir>  in ~8sec
> > more tries: time -p ls -l <5k+ entry dir>  in ~43sec
> >
> > Remounting the nfs-dir on the client resets the problem.
> >
> > Any ideas?
> 
> Ok, I played some more with this, and it turns out that nfsV3 is a lot 
> faster.  But, this does not explain why the 2.4.31 kernel is still over 
> 4-times faster than 2.6.23.
> 
> Can anybody explain what's going on?
> 

Sure, Neil can! ;)
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