Re: [PATCH 2/2] mm: Abort reclaim/compaction if compaction canproceed

From: Mel Gorman
Date: Fri Oct 07 2011 - 16:24:22 EST

On Fri, Oct 07, 2011 at 04:07:06PM -0400, Rik van Riel wrote:
> On 10/07/2011 11:17 AM, Mel Gorman wrote:
> >If compaction can proceed, shrink_zones() stops doing any work but
> >the callers still shrink_slab(), raises the priority and potentially
> >sleeps. This patch aborts direct reclaim/compaction entirely if
> >compaction can proceed.
> >
> >Signed-off-by: Mel Gorman<mgorman@xxxxxxx>
> This patch makes sense to me, but I have not tested it like
> the first one.

Do if you can.

> Mel, have you tested this patch?


> Did you see any changed
> behaviour vs. just the first patch?

It's marginal and could be confirmation bias on my part. Basically,
there is noise when this path is being exercised but there were fewer
slabs scanned. However, I don't know what the variances are and
whether the reduction was within the noise or not but it makes sense
that it would scan less. If I profiled carefully, I might be able
to show that a few additional cycles are spent raising the priority
but it would be marginal.

While patch 1 is very clear, patch 2 depends on reviewers deciding it
"makes sense".

> Having said that, I'm pretty sure the patch is ok :)

Care to ack?

Mel Gorman
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