Messages in this thread | | | Subject | Re: [PATCH 08/10] mm, page_alloc: Remove MIGRATE_RESERVE | From | Vlastimil Babka <> | Date | Wed, 29 Jul 2015 11:59:15 +0200 |
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On 07/20/2015 10:00 AM, Mel Gorman wrote: > From: Mel Gorman <mgorman@suse.de> > > MIGRATE_RESERVE preserves an old property of the buddy allocator that existed > prior to fragmentation avoidance -- min_free_kbytes worth of pages tended to > remain free until the only alternative was to fail the allocation. At the
^ I think you meant contiguous instead of free? Is it because splitting chooses lowest possible order, and grouping by mobility means you might be splitting e.g. order-5 movable page instead of using order-0 unmovable page? And that the fallback heuristics specifically select highest available order? I think it's not that obvious, so worth mentioning.
> time it was discovered that high-order atomic allocations relied on this > property so MIGRATE_RESERVE was introduced. A later patch will introduce > an alternative MIGRATE_HIGHATOMIC so this patch deletes MIGRATE_RESERVE > and supporting code so it'll be easier to review. Note that this patch > in isolation may look like a false regression if someone was bisecting > high-order atomic allocation failures. > > Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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