Re: [PATCH 0/7] Add RCU-walk support to NFS.

[NeilBrown <neilb@suse.de>]

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On Sun, 13 Jul 2014 22:00:12 -0400 Trond Myklebust
<trond.myklebust@primarydata.com> wrote:

> On Sun, Jul 13, 2014 at 9:28 PM, NeilBrown <neilb@suse.de> wrote:
> > NFS current abort and attempt at filename lookup in RCU mode.
> > This can have serious performance impact on a highly parallel load.
> >
> > The "Makefile" below generates just such a load.  On a 40-core
> > machine "make -j 40" is about 6 times as fast at "make -j 5"
> > when a local filesystem is used (e.g. XFS), but as much as half
> > as fast when NFS is used.
> > With this patch set, "make -j 40" is about 3 times as fast as
> > "make -j 5" on NFS, and "perf" data doesn't show spinlocks to be a big
> > problem any more.
> >
> > This is a re-submission with a few small improvements of a patch set
> > posted in March.  Since then I have recieved confirmation that it
> > definitely fixes the problem, when combined with a patch set which
> > enhances autofs4 in a similar way.  So it has had quite a bit of
> > testing.
> 
> Hi Neil,
> 
> What kind of tests have you personally (or SuSE if relevant) performed?
> Have you run this under NFSometer in order to check for regressions,
> and if so on what workloads?
> 
> The above are not requirements in order to get the patches into
> mainline, I'm just curious.

I hadn't come across NFSometer before, looks useful!

The only testing is that Makefile, and that was done mostly by the customer.

Further, that testing was a version of the patchset for Linux 3.0.
This particular patchset I've only tested lightly on my little 2-core test
machine.
I'm certainly happy to try beating on it a bit hard, and can see if I can get
access to an 80-core machine that I had a brief play with a while back and do
some more testing there.

NeilBrown

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