From: Nick Piggin <npiggin@suse.de>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@ozlabs.org, paulus@samba.org
Subject: Re: [patch 2/2] powerpc: replace isync with lwsync
Date: Wed, 4 Mar 2009 11:15:55 +0100 [thread overview]
Message-ID: <20090304101555.GD27043@wotan.suse.de> (raw)
In-Reply-To: <1236139451.6696.10.camel@pasglop>
On Wed, Mar 04, 2009 at 03:04:11PM +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2009-02-19 at 18:21 +0100, Nick Piggin wrote:
> > OK, here is this patch again. You didn't think I'd let a 2% performance
> > improvement be forgotten? :)
> >
> > Anyway, patch won't work well on architecture without lwsync, but I won't
> > bother fixing that kind of thing and making it merge worthy until you
> > guys say something positive about it.
> >
> > 20 runs of tbench on the G5
> >
> > unpatched AVG=920.37 STD=2.36
> > patched AVG=938.89 STD=3.33
> >
> > (throughput in MB/s) This is a 1.9% throughput increase.
>
> Definitely worth it believe. We could use a macro that uses michael new
> improvements on the CPU features code pathing so that the isync gets
> changed to lwsync on some CPUs based on the availability of it.
OK. I guess the interesting part about this is that I can't find any
IBM documentation for lwsync capable CPUs that suggest using this
pattern for acquire locking. It would be interesting to know whether
it helps other CPUs...
next prev parent reply other threads:[~2009-03-04 10:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-19 17:12 [patch 1/2] powerpc: optimise smp_mb Nick Piggin
2009-02-19 17:21 ` [patch 2/2] powerpc: replace isync with lwsync Nick Piggin
2009-03-04 4:04 ` Benjamin Herrenschmidt
2009-03-04 10:15 ` Nick Piggin [this message]
2009-03-04 4:03 ` [patch 1/2] powerpc: optimise smp_mb Benjamin Herrenschmidt
2009-03-04 9:38 ` Nick Piggin
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