[PATCH 0/4] (CMA_AGGRESSIVE) Make CMA memory be more aggressive about allocation

[Hui Zhu]

In fallbacks of page_alloc.c, MIGRATE_CMA is the fallback of
MIGRATE_MOVABLE.
MIGRATE_MOVABLE will use MIGRATE_CMA when it doesn't have a page in
order that Linux kernel want.

If a system that has a lot of user space program is running, for
instance, an Android board, most of memory is in MIGRATE_MOVABLE and
allocated.  Before function __rmqueue_fallback get memory from
MIGRATE_CMA, the oom_killer will kill a task to release memory when
kernel want get MIGRATE_UNMOVABLE memory because fallbacks of
MIGRATE_UNMOVABLE are MIGRATE_RECLAIMABLE and MIGRATE_MOVABLE.
This status is odd.  The MIGRATE_CMA has a lot free memory but Linux
kernel kill some tasks to release memory.

This patch series adds a new function CMA_AGGRESSIVE to make CMA memory
be more aggressive about allocation.
If function CMA_AGGRESSIVE is available, when Linux kernel call function
__rmqueue try to get pages from MIGRATE_MOVABLE and conditions allow,
MIGRATE_CMA will be allocated as MIGRATE_MOVABLE first.  If MIGRATE_CMA
doesn't have enough pages for allocation, go back to allocate memory from
MIGRATE_MOVABLE.
Then the memory of MIGRATE_MOVABLE can be kept for MIGRATE_UNMOVABLE and
MIGRATE_RECLAIMABLE which doesn't have fallback MIGRATE_CMA.

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