Messages in this thread | | | Date | Thu, 16 Oct 2014 01:55:46 -0700 | From | Laura Abbott <> | Subject | Re: [PATCH 0/4] (CMA_AGGRESSIVE) Make CMA memory be more aggressive about allocation |
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On 10/15/2014 8:35 PM, Hui Zhu wrote: > 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. >
It's good to see another proposal to fix CMA utilization. Do you have any data about the success rate of CMA contiguous allocation after this patch series? I played around with a similar approach of using CMA for MIGRATE_MOVABLE allocations and found that although utilization did increase, contiguous allocations failed at a higher rate and were much slower. I see what this series is trying to do with avoiding allocation from CMA pages when a contiguous allocation is progress. My concern is that there would still be problems with contiguous allocation after all the MIGRATE_MOVABLE fallback has happened.
Thanks, Laura
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