On Mon, 22 Feb 2010 15:15:13 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > On Mon, 22 Feb 2010 14:31:51 +0900 > Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote: > > > Hi. > > > > On Wed, 17 Feb 2010 11:34:30 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > On Tue, 16 Feb 2010 18:28:05 -0800 (PST) > > > David Rientjes <rientjes@xxxxxxxxxx> wrote: > > > > > > > On Wed, 17 Feb 2010, KAMEZAWA Hiroyuki wrote: > > > > > > > > > > What do you think about making pagefaults use out_of_memory() directly and > > > > > > respecting the sysctl_panic_on_oom settings? > > > > > > > > > > > > > > > > I don't think this patch is good. Because several memcg can > > > > > cause oom at the same time independently, system-wide oom locking is > > > > > unsuitable. BTW, what I doubt is much more fundamental thing. > > > > > > > > > > > > > We want to lock all populated zones with ZONE_OOM_LOCKED to avoid > > > > needlessly killing more than one task regardless of how many memcgs are > > > > oom. > > > > > > > Current implentation archive what memcg want. Why remove and destroy memcg ? > > > > > It might be a bit off-topic, but memcg's check for last_oom_jiffies seems > > not to work well under heavy load, and pagefault_out_of_memory() causes > > global oom. > > > > Step.1 make a memory cgroup directory and sed memory.limit_in_bytes to a small value > > > > > mkdir /cgroup/memory/test > > > echo 1M >/cgroup/memory/test/memory.limit_in_bytes > > > > Stem.2 run attached test program(which allocates memory and does fork recursively) > > > > > ./recursive_fork -c 8 -s `expr 1 \* 1024 \* 1024` > > > > This causes not only memcg's oom, but also global oom(My machine has 8 CPUS). > > > > === > > [348090.121808] recursive_fork3 invoked oom-killer: gfp_mask=0xd0, order=0, oom_adj=0 > > [348090.121821] recursive_fork3 cpuset=/ mems_allowed=0 > > [348090.121829] Pid: 22744, comm: recursive_fork3 Not tainted 2.6.32.8-00001-gb6cd517 #3 > > [348090.121832] Call Trace: > > [348090.121849] [<ffffffff810d6015>] oom_kill_process+0x86/0x295 > > [348090.121855] [<ffffffff810d64cf>] ? select_bad_process+0x63/0xf0 > > [348090.121861] [<ffffffff810d687a>] mem_cgroup_out_of_memory+0x69/0x87 > > [348090.121870] [<ffffffff811119c2>] __mem_cgroup_try_charge+0x15f/0x1d4 > > [348090.121876] [<ffffffff811126bc>] mem_cgroup_try_charge_swapin+0x104/0x159 > > [348090.121885] [<ffffffff810edd9b>] handle_mm_fault+0x4ca/0x76c > > [348090.121895] [<ffffffff8143419f>] ? do_page_fault+0x141/0x2da > > [348090.121904] [<ffffffff81087286>] ? trace_hardirqs_on+0xd/0xf > > [348090.121910] [<ffffffff8143419f>] ? do_page_fault+0x141/0x2da > > [348090.121915] [<ffffffff8143431c>] do_page_fault+0x2be/0x2da > > [348090.121922] [<ffffffff81432115>] page_fault+0x25/0x30 > > [348090.121929] Task in /test killed as a result of limit of /test > > [348090.121936] memory: usage 1024kB, limit 1024kB, failcnt 279335 > > [348090.121940] memory+swap: usage 4260kB, limit 9007199254740991kB, failcnt 0 > > [348090.121943] Mem-Info: > > [348090.121947] Node 0 DMA per-cpu: > > [348090.121952] CPU 0: hi: 0, btch: 1 usd: 0 > > [348090.121956] CPU 1: hi: 0, btch: 1 usd: 0 > > [348090.121960] CPU 2: hi: 0, btch: 1 usd: 0 > > [348090.121963] CPU 3: hi: 0, btch: 1 usd: 0 > > [348090.121967] CPU 4: hi: 0, btch: 1 usd: 0 > > [348090.121970] CPU 5: hi: 0, btch: 1 usd: 0 > > [348090.121974] CPU 6: hi: 0, btch: 1 usd: 0 > > [348090.121977] CPU 7: hi: 0, btch: 1 usd: 0 > > [348090.121980] Node 0 DMA32 per-cpu: > > [348090.121984] CPU 0: hi: 186, btch: 31 usd: 19 > > [348090.121988] CPU 1: hi: 186, btch: 31 usd: 11 > > [348090.121992] CPU 2: hi: 186, btch: 31 usd: 178 > > [348090.121995] CPU 3: hi: 186, btch: 31 usd: 0 > > [348090.121999] CPU 4: hi: 186, btch: 31 usd: 182 > > [348090.122002] CPU 5: hi: 186, btch: 31 usd: 29 > > [348090.122006] CPU 6: hi: 186, btch: 31 usd: 0 > > [348090.122009] CPU 7: hi: 186, btch: 31 usd: 0 > > [348090.122012] Node 0 Normal per-cpu: > > [348090.122016] CPU 0: hi: 186, btch: 31 usd: 54 > > [348090.122020] CPU 1: hi: 186, btch: 31 usd: 109 > > [348090.122023] CPU 2: hi: 186, btch: 31 usd: 149 > > [348090.122027] CPU 3: hi: 186, btch: 31 usd: 119 > > [348090.122030] CPU 4: hi: 186, btch: 31 usd: 123 > > [348090.122033] CPU 5: hi: 186, btch: 31 usd: 145 > > [348090.122037] CPU 6: hi: 186, btch: 31 usd: 54 > > [348090.122041] CPU 7: hi: 186, btch: 31 usd: 95 > > [348090.122049] active_anon:5354 inactive_anon:805 isolated_anon:0 > > [348090.122051] active_file:18317 inactive_file:57785 isolated_file:0 > > [348090.122053] unevictable:0 dirty:0 writeback:211 unstable:0 > > [348090.122054] free:3324478 slab_reclaimable:18860 slab_unreclaimable:13472 > > [348090.122056] mapped:4315 shmem:63 pagetables:1098 bounce:0 > > [348090.122059] Node 0 DMA free:15676kB min:12kB low:12kB high:16kB active_anon:0kB inacti > > ve_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated( > > file):0kB present:15100kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_re > > claimable:0kB slab_unreclaimable:16kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce: > > 0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no > > [348090.122076] lowmem_reserve[]: 0 3204 13932 13932 > > [348090.122083] Node 0 DMA32 free:2773244kB min:3472kB low:4340kB high:5208kB active_anon: > > 0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB > > isolated(file):0kB present:3281248kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem > > :0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable: > > 0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no > > [348090.122100] lowmem_reserve[]: 0 0 10728 10728 > > [348090.122108] Node 0 Normal free:10508992kB min:11624kB low:14528kB high:17436kB active_ > > anon:21416kB inactive_anon:3220kB active_file:73268kB inactive_file:231140kB unevictable:0 > > kB isolated(anon):0kB isolated(file):0kB present:10985984kB mlocked:0kB dirty:0kB writebac > > k:844kB mapped:17260kB shmem:252kB slab_reclaimable:75440kB slab_unreclaimable:53872kB ker > > nel_stack:1224kB pagetables:4392kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned > > :0 all_unreclaimable? no > > [348090.122125] lowmem_reserve[]: 0 0 0 0 > > [348090.122788] Node 0 DMA: 1*4kB 1*8kB 3*16kB 2*32kB 3*64kB 2*128kB 1*256kB 1*512kB 2*102 > > 4kB 2*2048kB 2*4096kB = 15676kB > > [348090.122853] Node 0 DMA32: 11*4kB 6*8kB 2*16kB 4*32kB 6*64kB 13*128kB 4*256kB 6*512kB 6 > > *1024kB 4*2048kB 672*4096kB = 2773244kB > > [348090.122915] Node 0 Normal: 188*4kB 128*8kB 214*16kB 409*32kB 107*64kB 18*128kB 4*256kB > > 1*512kB 2*1024kB 0*2048kB 2558*4096kB = 10508592kB > > [348090.122936] 76936 total pagecache pages > > [348090.122940] 816 pages in swap cache > > [348090.122943] Swap cache stats: add 7851711, delete 7850894, find 3676243/4307445 > > [348090.122946] Free swap = 1995492kB > > [348090.122949] Total swap = 2000888kB > > [348090.300467] 3670016 pages RAM > > [348090.300471] 153596 pages reserved > > [348090.300474] 38486 pages shared > > [348090.300476] 162081 pages non-shared > > [348090.300482] Memory cgroup out of memory: kill process 22072 (recursive_fork3) score 12 > > 48 or a child > > [348090.300486] Killed process 22072 (recursive_fork3) > > [348090.300524] Kernel panic - not syncing: out of memory from page fault. panic_on_oom is > > selected. > > [348090.300526] > > [348090.311038] Pid: 22744, comm: recursive_fork3 Not tainted 2.6.32.8-00001-gb6cd517 #3 > > [348090.311050] Call Trace: > > [348090.311073] [<ffffffff8142efa4>] panic+0x75/0x133 > > [348090.311090] [<ffffffff810d67d2>] pagefault_out_of_memory+0x50/0x8f > > [348090.311104] [<ffffffff81036a2d>] mm_fault_error+0x37/0xba > > [348090.311117] [<ffffffff8143428d>] do_page_fault+0x22f/0x2da > > [348090.311130] [<ffffffff81432115>] page_fault+0x25/0x30 > > === > > > > I take a kdump by enabling panic_on_oom, and compared the last_oom_jiffies and jiffies. > > > > crash> struct mem_cgroup.last_oom_jiffies 0xffffc90013514000 > > last_oom_jiffies = 4642757419, > > crash> p jiffies > > jiffies = $10 = 4642757607 > > > > I agree this is a extreme example, but this is not a desirable behavior. > > Changing "HZ/10" in mem_cgroup_last_oom_called() to "HZ/2" or some would fix > > this case, but it's not a essential fix. > > Yes, current design is not the best thing, my bad. > (I had to band-aid against unexpected panic in pagefault_out_of_memory.) > > But tweaking that vaule seems not promissing. > > Essential fix is better. The best fix is don't call oom-killer in > pagefault_out_of_memory. So, returning other than VM_FAULT_OOM is > the best, I think. But hmm...we don't have VM_FAULT_AGAIN etc.. > So, please avoid quick fix. > > One thing I can think of is sleep-and-retry in try_charge() if PF_MEMDIE > is not set. (But..By this, memcg will never return faiulre in page fault. > but it may sound reasonable.) > hmm, I can agree with you. But I think we need some trick to distinguish normal VM_FAULT_OOM and memcg's VM_FAULT_OOM(the current itself was killed by memcg's oom, so exited the retry) at mem_cgroup_oom_called() to avoid the system from panic when panic_on_oom is enabled. (Mark the task which is being killed by memcg's oom ?). Thanks, Daisuke Nishimura. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>