Messages in this thread | | | Date | Fri, 09 May 2014 14:39:20 +0200 | From | Marek Szyprowski <> | Subject | Re: [RFC PATCH 0/3] Aggressively allocate the pages on cma reserved memory |
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Hello,
On 2014-05-08 02:32, Joonsoo Kim wrote: > This series tries to improve CMA. > > CMA is introduced to provide physically contiguous pages at runtime > without reserving memory area. But, current implementation works like as > reserving memory approach, because allocation on cma reserved region only > occurs as fallback of migrate_movable allocation. We can allocate from it > when there is no movable page. In that situation, kswapd would be invoked > easily since unmovable and reclaimable allocation consider > (free pages - free CMA pages) as free memory on the system and free memory > may be lower than high watermark in that case. If kswapd start to reclaim > memory, then fallback allocation doesn't occur much. > > In my experiment, I found that if system memory has 1024 MB memory and > has 512 MB reserved memory for CMA, kswapd is mostly invoked around > the 512MB free memory boundary. And invoked kswapd tries to make free > memory until (free pages - free CMA pages) is higher than high watermark, > so free memory on meminfo is moving around 512MB boundary consistently. > > To fix this problem, we should allocate the pages on cma reserved memory > more aggressively and intelligenetly. Patch 2 implements the solution. > Patch 1 is the simple optimization which remove useless re-trial and patch 3 > is for removing useless alloc flag, so these are not important. > See patch 2 for more detailed description. > > This patchset is based on v3.15-rc4.
Thanks for posting those patches. It basically reminds me the following discussion: http://thread.gmane.org/gmane.linux.kernel/1391989/focus=1399524
Your approach is basically the same. I hope that your patches can be improved in such a way that they will be accepted by mm maintainers. I only wonder if the third patch is really necessary. Without it kswapd wakeup might be still avoided in some cases.
> Thanks. > Joonsoo Kim (3): > CMA: remove redundant retrying code in __alloc_contig_migrate_range > CMA: aggressively allocate the pages on cma reserved memory when not > used > CMA: always treat free cma pages as non-free on watermark checking > > include/linux/mmzone.h | 6 +++ > mm/compaction.c | 4 -- > mm/internal.h | 3 +- > mm/page_alloc.c | 117 +++++++++++++++++++++++++++++++++++++++--------- > 4 files changed, 102 insertions(+), 28 deletions(-) >
Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
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