Re: [rfc][patch] store-free path walking

Nick Piggin
2009-10-09T10:08:26Z

On Fri, Oct 09, 2009 at 10:54:52AM +0200, Jens Axboe wrote:
> On Thu, Oct 08 2009, Nick Piggin wrote:
> > This is actualy nice too. My tests were on a 2s8c Barcelona system,
> > but this is showing we have a nice serial win on Nehalem as well.
> > Actually K8 CPUs have a bit faster lock primitives than earlier
> > Intel CPUs I think (closer to Nehalem), so we might see an even
> > bigger win with a Core2.
>
> Ran it on another box. This isn't quite a core 2 though, it's a sparc64
> (Niagara 2). It has 64 threads, too, but just 8 cores.
>
> 2.6.32-rc3 serial
> real 0m5.390s
> user 0m1.340s
> sys 0m2.970s
>
> 2.6.32-rc3 parallel
> real 0m2.009s
> user 0m0.900s
> sys 0m2.490s
>
> vfs serial
> real 0m4.816s
> user 0m1.250s
> sys 0m2.270s
>
> vfs parallel
> real 0m1.967s
> user 0m0.920s
> sys 0m1.960s
>
> So it's a win-win there on that platform too.

That's nice to see it's really quite a good win in the serial case
on this CPU too.

Parallel interestingly not improved. Whether it is because the locks
are able to be bounced around much more quickly than on our multi
socket systems, or some quirk of the lots-of-chickens CPU that doesn't
take so well to the workload, I don't know. Maybe it's even the
fs->lock that will still be there in your patches.