On 2019/6/25 1:54, Michal Hocko wrote: > On Tue 25-06-19 00:47:11, zhong jiang wrote: >> On 2019/6/24 22:01, Michal Hocko wrote: >>> On Mon 24-06-19 21:11:55, zhong jiang wrote: >>>> [ 652.272622] sh invoked oom-killer: gfp_mask=0x26080c0, order=3, oom_score_adj=0 >>>> [ 652.272683] CPU: 0 PID: 1748 Comm: sh Tainted: P O 4.4.171 #8 >>>> [ 653.452827] Mem-Info: >>>> [ 653.466390] active_anon:20377 inactive_anon:187 isolated_anon:0 >>>> [ 653.466390] active_file:5087 inactive_file:4825 isolated_file:0 >>>> [ 653.466390] unevictable:12 dirty:0 writeback:32 unstable:0 >>>> [ 653.466390] slab_reclaimable:636 slab_unreclaimable:1754 >>>> [ 653.466390] mapped:5338 shmem:194 pagetables:231 bounce:0 >>>> [ 653.466390] free:1086 free_pcp:85 free_cma:0 >>>> [ 653.625286] Normal free:4248kB min:1696kB low:2120kB high:2544kB active_anon:81508kB inactive_anon:748kB active_file:20348kB inactive_file:19300kB unevictable:48kB isolated(anon):0kB isolated(file):0kB present:252928kB managed:180496kB mlocked:0kB dirty:0kB writeback:128kB mapped:21352kB shmem:776kB slab_reclaimable:2544kB slab_unreclaimable:7016kB kernel_stack:9856kB pagetables:924kB unstable:0kB bounce:0kB free_pcp:392kB local_pcp:392kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no >>>> [ 654.177121] lowmem_reserve[]: 0 0 0 >>>> [ 654.462015] Normal: 752*4kB (UME) 128*8kB (UM) 21*16kB (M) 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 4368kB >>>> [ 654.601093] 10132 total pagecache pages >>>> [ 654.606655] 63232 pages RAM >>> [...] >>>>>> As the process is created, kernel stack will use the higher order to allocate continuous memory. >>>>>> Due to the fragmentabtion, we fails to allocate the memory. And the low memory will result >>>>>> in hardly memory compction. hence, it will easily to reproduce the oom. >>>>> How get your get such a large fragmentation that you cannot allocate >>>>> order-1 pages and compaction is not making any progress? >>>> >From the above oom report, we can see that there is not order-2 pages. It wil hardly to allocate kernel stack when >>>> creating the process. And we can easily to reproduce the situation when runing some userspace program. >>>> >>>> But it rarely trigger the oom when It do not introducing the highatomic. we test that in the kernel 3.10. >>> I do not really see how highatomic reserves could make any difference. >>> We do drain them before OOM killer is invoked. The above oom report >>> confirms that there is indeed no order-3+ free page to be used. >> I mean that all order with migrate_highatomic is alway zero, it can be true that > Yes, highatomic is meant to be used for higher order allocations which > already do have access to memory reserves. E.g. via __GFP_ATOMIC. If current kernel have not use __GFP_ATOMIC to allocate memory, highatomic will have not available higher order. And we have order-3 kernel stack allocation requirement in the system. There is not memory reserve to use for us in the emergency situation, which is different from migrate_reserve. Maybe I think that we can change the reserve memory behaviour, Not only reserve higher order in GFP_ATOMIC. Thanks, zhong jiang
