linux-kernel - Re: [PATCH v5]: Improve performance of LZO hibernation

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Date:	Wed, 28 Sep 2011 17:57:29 +1000
From:	Bojan Smojver <bojan@...ursive.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH v5]: Improve performance of LZO hibernation

On Wed, 2011-09-28 at 10:48 +0300, Pekka Enberg wrote:
> > We want to keep at least one CPU free for that I/O and for pulling
> the
> > other threads into sync when they are done (that is if we have more
> than
> > one), right?
> 
> Well, dunno if it matters much. Did you see performance improvement
> with that?

Haven't tried, to be honest. Just thought it may make sense.

> Is the CPU binding really needed?

Don't really know, but I would think it would help with
compression/decompression code. We don't want these threads bouncing
between CPUs unless they have to. I would guess the caches would work
better that way and all that.

Again, just guessing.

> Anyway, if you want to keep the existing behavior, maybe something
> like
> 
> nr_other_cpus = min(1, num_online_cpus()-1);
> 
> nr_threads = min(nr_other_cpus, LZO_THREADS);
> 
> would do the trick?

Yeah, makes sense. The first one should be max() though.

-- 
Bojan

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