Messages in this thread | | | From | Hui Zhu <> | Subject | [PATCH 0/4] (CMA_AGGRESSIVE) Make CMA memory be more aggressive about allocation | Date | Thu, 16 Oct 2014 11:35:47 +0800 |
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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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