> Neil Brown wrote:
> > On Tuesday November 6,
akpm@linux-foundation.org wrote:
> > > > On Tue, 6 Nov 2007 14:28:11 +0300 Al Boldi <a1426z@gawab.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! ;)
>
> Thanks Andrew!
>
> > Nuh.
> > He said "userland rpc.nfs.Vx". I only do "kernel-land NFS". In these
> > days of high specialisation, each line of code is owned by a different
> > person, and finding the right person is hard....
> >
> > I would suggest getting a 'tcpdump -s0' trace and seeing (with
> > wireshark) what is different between the various cases.
>
> Thanks Neil for looking into this. Your suggestion has already been answered
> in a previous post, where the difference has been attributed to "ls -l"
> inducing lookup for the first try, which is fast, and getattr for later
> tries, which is super-slow.
>
> Now it's easy to blame the userland rpc.nfs.V2 server for this, but what's
> not clear is how come 2.4.31 handles getattr faster than 2.6.23?
>
