Re: [PATCHv21 08/16] mm: mmzone: MIGRATE_CMA migration type added

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>]

On Fri, 10 Feb 2012 18:32:23 +0100
Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote:

> From: Michal Nazarewicz <mina86@xxxxxxxxxx>
> 
> The MIGRATE_CMA migration type has two main characteristics:
> (i) only movable pages can be allocated from MIGRATE_CMA
> pageblocks and (ii) page allocator will never change migration
> type of MIGRATE_CMA pageblocks.
> 
> This guarantees (to some degree) that page in a MIGRATE_CMA page
> block can always be migrated somewhere else (unless there's no
> memory left in the system).
> 
> It is designed to be used for allocating big chunks (eg. 10MiB)
> of physically contiguous memory.  Once driver requests
> contiguous memory, pages from MIGRATE_CMA pageblocks may be
> migrated away to create a contiguous block.
> 
> To minimise number of migrations, MIGRATE_CMA migration type
> is the last type tried when page allocator falls back to other
> migration types when requested.
> 
> Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> Acked-by: Mel Gorman <mel@xxxxxxxxx>
> Tested-by: Rob Clark <rob.clark@xxxxxxxxxx>
> Tested-by: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
> Tested-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>


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