Re: [patch 7/8] mm: vmscan: compaction works against zones, notlruvecs

From: Mel Gorman
Date: Thu Dec 13 2012 - 06:12:47 EST

On Wed, Dec 12, 2012 at 04:43:39PM -0500, Johannes Weiner wrote:
> The restart logic for when reclaim operates back to back with
> compaction is currently applied on the lruvec level. But this does
> not make sense, because the container of interest for compaction is a
> zone as a whole, not the zone pages that are part of a certain memory
> cgroup.
> Negative impact is bounded. For one, the code checks that the lruvec
> has enough reclaim candidates, so it does not risk getting stuck on a
> condition that can not be fulfilled. And the unfairness of hammering
> on one particular memory cgroup to make progress in a zone will be
> amortized by the round robin manner in which reclaim goes through the
> memory cgroups. Still, this can lead to unnecessary allocation
> latencies when the code elects to restart on a hard to reclaim or
> small group when there are other, more reclaimable groups in the zone.
> Move this logic to the zone level and restart reclaim for all memory
> cgroups in a zone when compaction requires more free pages from it.
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>

Acked-by: Mel Gorman <mgorman@xxxxxxx>

Mel Gorman
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