On Sat 08-10-16 00:04:25, Minchan Kim wrote: [...] > I can show other log which reserve greater than 1%. See the DMA32 zone > free pages. It was GFP_ATOMIC allocation so it's different with I posted > but important thing is VM can reserve memory greater than 1% by the race > which was really what we want. > > in:imklog: page allocation failure: order:0, mode:0x2280020(GFP_ATOMIC|__GFP_NOTRACK) [...] > DMA: 7*4kB (UE) 3*8kB (UH) 1*16kB (M) 0*32kB 2*64kB (U) 1*128kB (M) 1*256kB (U) 0*512kB 1*1024kB (U) 1*2048kB (U) 1*4096kB (H) = 7748kB > DMA32: 10*4kB (H) 3*8kB (H) 47*16kB (H) 38*32kB (H) 5*64kB (H) 1*128kB (H) 2*256kB (H) 3*512kB (H) 3*1024kB (H) 3*2048kB (H) 4*4096kB (H) = 30128kB Yes, this sounds like a bug. Please add this information to the patch which aims to fix the misaccounting. > > So while I do agree that potential issues - misaccounting and others you > > are addressing in the follow up patch - are good to fix but I believe that > > draining last 19M is not something that would reliably get you over the > > edge. Your workload (93% of memory sitting on anon LRU with swap full) > > simply doesn't fit into the amount of memory you have available. > > What happens if the workload fit into additional 19M memory? > I admit my testing aimed for proving the problem but with this patchset, > there is no OOM killing with many free pages and the number of OOM was > reduced highly. It is definitely better than old. > > Please don't ignore 1% memory in embedded system. 20M memory in 2G system, > If we can use those for zram, it is 60~80M memory via compression. > You should know how many engineers try to reduce 1M of their driver to > cost down of the product, seriously. I am definitely not ignoring neither embedded systems nor 1% of the memory that might really matter. I just wanted to point out that being that close to OOM usually blows up later or starts trashing very soon. It is true that a particular workload might benefit from ever last allocatable page in the system but it would be better to mention all that in the changelog. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>