Michal Hocko wrote: > On Thu 11-06-15 22:12:40, Tetsuo Handa wrote: > > Michal Hocko wrote: > [...] > > > > The moom_work used by SysRq-f sometimes cannot be executed > > > > because some work which is processed before the moom_work is processed is > > > > stalled for unbounded amount of time due to looping inside the memory > > > > allocator. > > > > > > Wouldn't wq code pick up another worker thread to execute the work. > > > There is also a rescuer thread as the last resort AFAIR. > > > > > > > Below is an example of moom_work lockup in v4.1-rc7 from > > http://I-love.SAKURA.ne.jp/tmp/serial-20150611.txt.xz > > > > ---------- > > [ 171.710406] sysrq: SysRq : Manual OOM execution > > [ 171.720193] kworker/2:9 invoked oom-killer: gfp_mask=0xd0, order=0, oom_score_adj=0 > > [ 171.722699] kworker/2:9 cpuset=/ mems_allowed=0 > > [ 171.724603] CPU: 2 PID: 11016 Comm: kworker/2:9 Not tainted 4.1.0-rc7 #3 > > [ 171.726817] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013 > > [ 171.729727] Workqueue: events moom_callback > > (...snipped...) > > [ 258.302016] sysrq: SysRq : Manual OOM execution > > Wow, this is a _lot_. I was aware that workqueues might be overloaded. > We have seen that in real loads and that led to > http://marc.info/?l=linux-kernel&m=141456398425553 wher the rescuer > didn't handle pending work properly. I thought that the fix helped in > the end. But 1.5 minutes is indeed unexpected for me. Excuse me, but you misunderstood the log. The logs for uptime = 171 and uptime = 258 are cases where SysRq-f (indicated by "sysrq: SysRq : Manual OOM execution" message) immediately invoked the OOM killer (indicated by "invoked oom-killer: gfp_mask=0xd0, order=0, oom_score_adj=0" message). What you should check is uptime > 301. Until I do SysRq-b at uptime = 707, the "sysrq: SysRq : Manual OOM execution" message is printed but the "invoked oom-killer: gfp_mask=0xd0, order=0, oom_score_adj=0" message is not printed. During this period (so far 5 minutes, presumably forever), moom_callback() remained pending. > > This of course disqualifies DELAYED_WORK for anything that has at least > reasonable time expectations which is the case here. -- 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>