| Message ID | 1683782550-25799-1-git-send-email-zhaoyang.huang@unisoc.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [PATCHv5] mm: optimization on page allocation when CMA enabled | expand |
On Thu, 11 May 2023 13:22:30 +0800 "zhaoyang.huang" <zhaoyang.huang@unisoc.com> wrote: > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com> > > Let us look at the timeline of scenarios below with WMARK_LOW=25MB WMARK_MIN=5MB > (managed pages 1.9GB). We can find that CMA begin to be used until 'C' under the > method of 'fixed 2 times of free cma over free pages' which could have the > scenario 'A' and 'B' into a fault state, that is, free UNMOVABLE & RECLAIMABLE > pages is lower than corresponding watermark without reclaiming which should be > deemed as against current memory policy. This commit try to solve this by > checking zone_watermark_ok again with removing CMA pages which could lead to a > proper time point of CMA's utilization. > > -- Free_pages > | > | > -- WMARK_LOW > | > -- Free_CMA > | > | > -- > > Free_CMA/Free_pages(MB) A(12/30) --> B(12/25) --> C(12/20) > fixed 1/2 ratio N N Y > this commit Y Y Y > Roman previously asked : Also I'm a bit concerned about potential performance implications. : Would be great to provide some benchmarks or some data. Probably it's : ok because of we have pcp caches on top, but I'm not 100% sure. Are you able to perform such testing and tell us the result? Thanks.
On Sat, Oct 7, 2023 at 5:17 AM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Thu, 11 May 2023 13:22:30 +0800 "zhaoyang.huang" <zhaoyang.huang@unisoc.com> wrote: > > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com> > > > > Let us look at the timeline of scenarios below with WMARK_LOW=25MB WMARK_MIN=5MB > > (managed pages 1.9GB). We can find that CMA begin to be used until 'C' under the > > method of 'fixed 2 times of free cma over free pages' which could have the > > scenario 'A' and 'B' into a fault state, that is, free UNMOVABLE & RECLAIMABLE > > pages is lower than corresponding watermark without reclaiming which should be > > deemed as against current memory policy. This commit try to solve this by > > checking zone_watermark_ok again with removing CMA pages which could lead to a > > proper time point of CMA's utilization. > > > > -- Free_pages > > | > > | > > -- WMARK_LOW > > | > > -- Free_CMA > > | > > | > > -- > > > > Free_CMA/Free_pages(MB) A(12/30) --> B(12/25) --> C(12/20) > > fixed 1/2 ratio N N Y > > this commit Y Y Y > > > > Roman previously asked > > : Also I'm a bit concerned about potential performance implications. > : Would be great to provide some benchmarks or some data. Probably it's > : ok because of we have pcp caches on top, but I'm not 100% sure. > > Are you able to perform such testing and tell us the result? I have applied this patch in a v5.4 based ANDROID system and got no regression problem. Actually, this commit is aimed to have alloc_pages(GFP_USER) use CMA instead of stealing U&R(could lead to GFP_KERNEL fail) only when zone's free pages and free cma are around WATERMARK_LOW/MIN which would NOT affect most scenarios. > > Thanks. >
On Sun, 8 Oct 2023 15:54:40 +0800 Zhaoyang Huang <huangzhaoyang@gmail.com> wrote: > > Roman previously asked > > > > : Also I'm a bit concerned about potential performance implications. > > : Would be great to provide some benchmarks or some data. Probably it's > > : ok because of we have pcp caches on top, but I'm not 100% sure. > > > > Are you able to perform such testing and tell us the result? > I have applied this patch in a v5.4 based ANDROID system and got no > regression problem. Actually, this commit is aimed to have > alloc_pages(GFP_USER) use CMA instead of stealing U&R(could lead to > GFP_KERNEL fail) only when zone's free pages and free cma are around > WATERMARK_LOW/MIN which would NOT affect most scenarios. OK, thanks. Could the appropriate people please take a look at this? It has been in mm-unstable since May. Thanks.
On Mon, Oct 09, 2023 at 05:14:15PM -0700, Andrew Morton wrote: > On Sun, 8 Oct 2023 15:54:40 +0800 Zhaoyang Huang <huangzhaoyang@gmail.com> wrote: > > > > Roman previously asked > > > > > > : Also I'm a bit concerned about potential performance implications. > > > : Would be great to provide some benchmarks or some data. Probably it's > > > : ok because of we have pcp caches on top, but I'm not 100% sure. > > > > > > Are you able to perform such testing and tell us the result? > > I have applied this patch in a v5.4 based ANDROID system and got no > > regression problem. Actually, this commit is aimed to have > > alloc_pages(GFP_USER) use CMA instead of stealing U&R(could lead to > > GFP_KERNEL fail) only when zone's free pages and free cma are around > > WATERMARK_LOW/MIN which would NOT affect most scenarios. > > OK, thanks. > > Could the appropriate people please take a look at this? It has been > in mm-unstable since May. I have 2 concerns: 1) it's still hard to understand the commit message and comments, I can only reverse-engineer it based on the code changes; 2) performance concerns I expressed earlier are not addressed. Idk what's a good benchmark for the page allocator, probably something i/o or networking heavy. On the positive side I believe that the patch is solving a real problem.
On Tue, Oct 10, 2023 at 9:31 AM Roman Gushchin <roman.gushchin@linux.dev> wrote: > > On Mon, Oct 09, 2023 at 05:14:15PM -0700, Andrew Morton wrote: > > On Sun, 8 Oct 2023 15:54:40 +0800 Zhaoyang Huang <huangzhaoyang@gmail.com> wrote: > > > > > > Roman previously asked > > > > > > > > : Also I'm a bit concerned about potential performance implications. > > > > : Would be great to provide some benchmarks or some data. Probably it's > > > > : ok because of we have pcp caches on top, but I'm not 100% sure. > > > > > > > > Are you able to perform such testing and tell us the result? > > > I have applied this patch in a v5.4 based ANDROID system and got no > > > regression problem. Actually, this commit is aimed to have > > > alloc_pages(GFP_USER) use CMA instead of stealing U&R(could lead to > > > GFP_KERNEL fail) only when zone's free pages and free cma are around > > > WATERMARK_LOW/MIN which would NOT affect most scenarios. > > > > OK, thanks. > > > > Could the appropriate people please take a look at this? It has been > > in mm-unstable since May. > > I have 2 concerns: > 1) it's still hard to understand the commit message and comments, I can > only reverse-engineer it based on the code changes; > 2) performance concerns I expressed earlier are not addressed. Idk what's > a good benchmark for the page allocator, probably something i/o or > networking heavy. > ok, I will update the commit message > On the positive side I believe that the patch is solving a real problem.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0745aed..4719800 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3071,6 +3071,43 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, } +#ifdef CONFIG_CMA +/* + * GFP_MOVABLE allocation could drain UNMOVABLE & RECLAIMABLE page blocks via + * the help of CMA which makes GFP_KERNEL failed. Checking if zone_watermark_ok + * again without ALLOC_CMA to see if to use CMA first. + */ +static bool use_cma_first(struct zone *zone, unsigned int order, unsigned int alloc_flags) +{ + unsigned long watermark; + bool cma_first = false; + + watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); + /* check if GFP_MOVABLE pass previous zone_watermark_ok via the help of CMA */ + if (zone_watermark_ok(zone, order, watermark, 0, alloc_flags & (~ALLOC_CMA))) { + /* + * Balance movable allocations between regular and CMA areas by + * allocating from CMA when over half of the zone's free memory + * is in the CMA area. + */ + cma_first = (zone_page_state(zone, NR_FREE_CMA_PAGES) > + zone_page_state(zone, NR_FREE_PAGES) / 2); + } else { + /* + * watermark failed means UNMOVABLE & RECLAIMBLE is not enough + * now, we should use cma first to keep them stay around the + * corresponding watermark + */ + cma_first = true; + } + return cma_first; +} +#else +static bool use_cma_first(struct zone *zone, unsigned int order, unsigned int alloc_flags) +{ + return false; +} +#endif /* * Do the hard work of removing an element from the buddy allocator. * Call me with the zone->lock already held. @@ -3084,12 +3121,11 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, if (IS_ENABLED(CONFIG_CMA)) { /* * Balance movable allocations between regular and CMA areas by - * allocating from CMA when over half of the zone's free memory - * is in the CMA area. + * allocating from CMA base on judging zone_watermark_ok again + * to see if the latest check got pass via the help of CMA */ if (alloc_flags & ALLOC_CMA && - zone_page_state(zone, NR_FREE_CMA_PAGES) > - zone_page_state(zone, NR_FREE_PAGES) / 2) { + use_cma_first(zone, order, alloc_flags)) { page = __rmqueue_cma_fallback(zone, order); if (page) return page;