On Thu, May 11, 2023 at 6:08 AM Roman Gushchin <roman.gushchin@xxxxxxxxx> wrote: > > On Wed, May 10, 2023 at 10:20:51AM +0800, zhaoyang.huang wrote: > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > > > Let us look at the series of scenarios below with WMARK_LOW=25MB,WMARK_MIN=5MB > > (managed pages 1.9GB). We can know that current 'fixed 1/2 ratio' start to use > > CMA since C which actually has caused U&R lower than WMARK_LOW (this should be > > deemed as against current memory policy, that is, UNMOVABLE & RECLAIMABLE should > > either stay around WATERMARK_LOW when no allocation or do reclaim via entering > > slowpath) > > > > -- 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 > > > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > I'm mostly fine with the code. The commit message is still very confusing to me, > not sure I understand what exactly this table means. And you still use "U&R". I would like to highlight the scenario "A&B" where the previous fixed 1/2 ratio introduces over use of UNMOVABLE & RECLAIMABLE. I will try to make it more clear by v5 > > 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. This patch helps solve my OOM issue in v5.15. Actually, It inherit the logic of 1/2 ratio and just behave differently when free pages is around corresponding watermark > > Thanks!
