On Mon, Jun 12, 2023 at 5:29 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 10.06.23 00:35, Andrew Morton wrote: > > On Wed, 31 May 2023 10:51:01 +0800 "zhaoyang.huang" <zhaoyang.huang@xxxxxxxxxx> wrote: > > > >> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > >> > >> This patch fixes unproductive reclaiming of CMA pages by skipping them when they > >> are not available for current context. It is arise from bellowing OOM issue, which > >> caused by large proportion of MIGRATE_CMA pages among free pages. > >> > >> [ 36.172486] [03-19 10:05:52.172] ActivityManager: page allocation failure: order:0, mode:0xc00(GFP_NOIO), nodemask=(null),cpuset=foreground,mems_allowed=0 > >> [ 36.189447] [03-19 10:05:52.189] DMA32: 0*4kB 447*8kB (C) 217*16kB (C) 124*32kB (C) 136*64kB (C) 70*128kB (C) 22*256kB (C) 3*512kB (C) 0*1024kB 0*2048kB 0*4096kB = 35848kB > >> [ 36.193125] [03-19 10:05:52.193] Normal: 231*4kB (UMEH) 49*8kB (MEH) 14*16kB (H) 13*32kB (H) 8*64kB (H) 2*128kB (H) 0*256kB 1*512kB (H) 0*1024kB 0*2048kB 0*4096kB = 3236kB > >> ... > >> [ 36.234447] [03-19 10:05:52.234] SLUB: Unable to allocate memory on node -1, gfp=0xa20(GFP_ATOMIC) > >> [ 36.234455] [03-19 10:05:52.234] cache: ext4_io_end, object size: 64, buffer size: 64, default order: 0, min order: 0 > >> [ 36.234459] [03-19 10:05:52.234] node 0: slabs: 53,objs: 3392, free: 0 > >> > > > > We saw plenty of feedback for earlier versions, but now silence. Does > > this mean we're all OK with v5? > > The logic kind-of makes sense to me (but the kswapd special-casing > already shows that it might be a bit fragile for future use), but I did > not yet figure out if this actually fixes something or is a pure > performance improvement. > > As we phrased it in the comment "It is waste of effort", but in the > patch description "This patch fixes unproductive reclaiming" + a scary > dmesg. > > Am I correct that this is a pure performance optimization (and the issue > revealed itself in that OOM report), or does this actually *fix* something? > > If it's a performance improvement, it would be good to show that it is > an actual improvement worth the churn ... Sorry for the confusion. As for the OOM issue, the previous commit(https://lkml.kernel.org/r/1683782550-25799-1-git-send-email-zhaoyang.huang@xxxxxxxxxx) helps to decrease the fail rate from 12/20 to 2/20, which it turn to be 0 when applying this patch. > > -- > Cheers, > > David / dhildenb >
