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SubjectRe: [PATCH] mm: cma: Discard clean pages during contiguous allocation instead of migration
On Tue, Sep 11, 2012 at 09:41:52AM +0900, Minchan Kim wrote:
> This patch drops clean cache pages instead of migration during
> alloc_contig_range() to minimise allocation latency by reducing the amount
> of migration is necessary. It's useful for CMA because latency of migration
> is more important than evicting the background processes working set.
> In addition, as pages are reclaimed then fewer free pages for migration
> targets are required so it avoids memory reclaiming to get free pages,
> which is a contributory factor to increased latency.
>
> * from v1
> * drop migrate_mode_t
> * add reclaim_clean_pages_from_list instad of MIGRATE_DISCARD support - Mel
>
> I measured elapsed time of __alloc_contig_migrate_range which migrates
> 10M in 40M movable zone in QEMU machine.
>
> Before - 146ms, After - 7ms
>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: Rik van Riel <riel@redhat.com>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

My signed-off is already on this but in earlier versions I was still
asking for changes. This time the patch looks good to me so even though
it is a bit redundant.

Reviewed-by: Mel Gorman <mgorman@suse.de>

Thanks Minchan.

--
Mel Gorman
SUSE Labs


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