Re: [PATCH 04/10] mm: vmscan: Decide whether to compact the pgdatbased on reclaim progress

From: Rik van Riel
Date: Thu Apr 11 2013 - 22:47:51 EST

On 04/09/2013 07:06 AM, Mel Gorman wrote:
In the past, kswapd makes a decision on whether to compact memory after the
pgdat was considered balanced. This more or less worked but it is late to
make such a decision and does not fit well now that kswapd makes a decision
whether to exit the zone scanning loop depending on reclaim progress.

This patch will compact a pgdat if at least the requested number of pages
were reclaimed from unbalanced zones for a given priority. If any zone is
currently balanced, kswapd will not call compaction as it is expected the
necessary pages are already available.

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>

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

This has the potential to increase kswapd cpu use, but probably at
the benefit of making reclaim run a little more smoothly. It should
help that compaction is only called when enough pages have been

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