NFS server bottlenecks

[Rick Macklem]

Ivan Voras wrote:
> On 20 October 2012 13:42, Nikolay Denev <ndenev at gmail.com> wrote:
> 
> > Here are the results from testing both patches :
> > http://home.totalterror.net/freebsd/nfstest/results.html
> > Both tests ran for about 14 hours ( a bit too much, but I wanted to
> > compare different zfs recordsize settings ),
> > and were done first after a fresh reboot.
> > The only noticeable difference seems to be much more context
> > switches with Ivan's patch.
> 
> Thank you very much for your extensive testing!
> 
> I don't know how to interpret the rise in context switches; as this is
> kernel code, I'd expect no context switches. I hope someone else can
> explain.
> 
> But, you have also shown that my patch doesn't do any better than
> Rick's even on a fairly large configuration, so I don't think there's
> value in adding the extra complexity, and Rick knows NFS much better
> than I do.
> 
> But there are a few things other than that I'm interested in: like why
> does your load average spike almost to 20-ties, and how come that with
> 24 drives in RAID-10 you only push through 600 MBit/s through the 10
> GBit/s Ethernet. Have you tested your drive setup locally (AESNI
> shouldn't be a bottleneck, you should be able to encrypt well into
> Gbyte/s range) and the network?
> 
> If you have the time, could you repeat the tests but with a recent
> Samba server and a CIFS mount on the client side? This is probably not
> important, but I'm just curious of how would it perform on your
> machine.

Oh, I realized that, if you are testing 9/stable (and not head), that
you won't have r227809. Without that, all reads on a given file will
be serialized, because the server will acquire an exclusive lock on
the vnode.

The patch for r227809 in head is at:
  http://people.freebsd.org/~rmacklem/lkshared.patch
This should apply fine to a 9 system (but not 8.n), I think.

Good luck with it and have fun, rick

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