Re: [PATCH 03/10] mm: vmscan: Flatten kswapd priority loop

[Johannes Weiner]

On Thu, Apr 11, 2013 at 08:57:51PM +0100, Mel Gorman wrote:
> kswapd stops raising the scanning priority when at least SWAP_CLUSTER_MAX
> pages have been reclaimed or the pgdat is considered balanced. It then
> rechecks if it needs to restart at DEF_PRIORITY and whether high-order
> reclaim needs to be reset. This is not wrong per-se but it is confusing
> to follow and forcing kswapd to stay at DEF_PRIORITY may require several
> restarts before it has scanned enough pages to meet the high watermark even
> at 100% efficiency. This patch irons out the logic a bit by controlling
> when priority is raised and removing the "goto loop_again".
> 
> This patch has kswapd raise the scanning priority until it is scanning
> enough pages that it could meet the high watermark in one shrink of the
> LRU lists if it is able to reclaim at 100% efficiency. It will not raise
> the scanning prioirty higher unless it is failing to reclaim any pages.
> 
> To avoid infinite looping for high-order allocation requests kswapd will
> not reclaim for high-order allocations when it has reclaimed at least
> twice the number of pages as the allocation request.
> 
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
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