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

[Mel Gorman <mgorman@suse.de>]

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@suse.de>
> 
> 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?

Yes.

> 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
SUSE Labs