Michal Hocko wrote: > On Fri 30-06-17 09:14:22, Tetsuo Handa wrote: > [...] > > Ping? Ping? When are we going to apply this patch or watchdog patch? > > This problem occurs with not so insane stress like shown below. > > I can't test almost OOM situation because test likely falls into either > > printk() v.s. oom_lock lockup problem or this too_many_isolated() problem. > > So you are saying that the patch fixes this issue. Do I understand you > corretly? And you do not see any other negative side effectes with it > applied? I hit this problem using http://lkml.kernel.org/r/20170626130346.26314-1-mhocko@xxxxxxxxxx on next-20170628. We won't be able to test whether the patch fixes this issue without seeing any other negative side effects without sending this patch to linux-next.git. But at least we know that even this patch is sent to linux-next.git, we will still see bugs like http://lkml.kernel.org/r/201703031948.CHJ81278.VOHSFFFOOLJQMt@xxxxxxxxxxxxxxxxxxx . > > I am sorry I didn't have much time to think about feedback from Johannes > yet. A more robust throttling method is surely due but also not trivial. > So I am not sure how to proceed. It is true that your last test case > with only 10 processes fighting resembles the reality much better than > hundreds (AFAIR) that you were using previously. Even if hundreds are running, most of them are simply blocked inside open() at down_write() (like an example from serial-20170423-2.txt.xz shown below). Actual number of processes fighting for memory is always less than 100. ? __schedule+0x1d2/0x5a0 ? schedule+0x2d/0x80 ? rwsem_down_write_failed+0x1f9/0x370 ? walk_component+0x43/0x270 ? call_rwsem_down_write_failed+0x13/0x20 ? down_write+0x24/0x40 ? path_openat+0x670/0x1210 ? do_filp_open+0x8c/0x100 ? getname_flags+0x47/0x1e0 ? do_sys_open+0x121/0x200 ? do_syscall_64+0x5c/0x140 ? entry_SYSCALL64_slow_path+0x25/0x25 > > Rik, Johannes what do you think? Should we go with the simpler approach > for now and think of a better plan longterm? I don't hurry if we can check using watchdog whether this problem is occurring in the real world. I have to test corner cases because watchdog is missing. Watchdog does not introduce negative side effects, will avoid soft lockups like http://lkml.kernel.org/r/CAM_iQpWuPVGc2ky8M-9yukECtS+zKjiDasNymX7rMcBjBFyM_A@xxxxxxxxxxxxxx , will avoid console_unlock() v.s. oom_lock mutext lockups due to warn_alloc(), will catch similar bugs which people are failing to reproduce. -- 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>
