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

From: Rik van Riel
Date: Fri Oct 07 2011 - 18:42:55 EST

On 10/07/2011 04:24 PM, Mel Gorman wrote:
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.

I'll probably build a kernel with your patch in it on
Sunday - I'll be walking across a mountain tomorrow :)

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.

This seems clear enough.

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?


Acked-by: Rik van Riel <riel@xxxxxxxxxx>

All rights reversed
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at