Re: [patch] Cache align futex hash buckets

[Ravikiran G Thirumalai <kiran@scalex86.org>]

On Mon, Feb 20, 2006 at 05:09:40PM -0800, Andrew Morton wrote:
> Ravikiran G Thirumalai <kiran@scalex86.org> wrote:
> >
> > 
> > Yes, only on vSMPowered systems.  Well, we have a large 
> > internode cacheline, but these machines have lots of memory too.  I 
> > thought a  simpler padding solution might be acceptable as futex_queues 
> > would be large only on our boxes.
> 
> Well it's your architecture...  As long as you're finding this to be a
> sufficiently large problem in testing to justify consuming a meg of memory
> then fine, let's do it.
> 
> But your initial changelog was rather benchmark-free?  It's always nice to
> see numbers accompanying a purported optimisation patch.

We saw 30% better elapsed time with a threaded benchmark on our systems, with 
this patch.  That said, we would like to avoid this bloat on our systems too, 
and some work needs to be done to improve futex hashing on NUMA.  But for now, 
this patch should be good enough.

Thanks,
Kiran