On 26/01/2019 02:41, Roman Gushchin wrote: > On Fri, Jan 25, 2019 at 08:47:57PM +0100, Arkadiusz Miśkiewicz wrote: >> On 25/01/2019 17:37, Tejun Heo wrote: >>> On Fri, Jan 25, 2019 at 08:52:11AM +0100, Arkadiusz Miśkiewicz wrote: >>>> On 24/01/2019 12:21, Arkadiusz Miśkiewicz wrote: >>>>> On 17/01/2019 14:17, Arkadiusz Miśkiewicz wrote: >>>>>> On 17/01/2019 13:25, Aleksa Sarai wrote: >>>>>>> On 2019-01-17, Arkadiusz Miśkiewicz <a.miskiewicz@xxxxxxxxx> wrote: >>>>>>>> Using kernel 4.19.13. >>>>>>>> >>>>>>>> For one cgroup I noticed weird behaviour: >>>>>>>> >>>>>>>> # cat pids.current >>>>>>>> 60 >>>>>>>> # cat cgroup.procs >>>>>>>> # >>>>>>> >>>>>>> Are there any zombies in the cgroup? pids.current is linked up directly >>>>>>> to __put_task_struct (so exit(2) won't decrease it, only the task_struct >>>>>>> actually being freed will decrease it). >>>>>>> >>>>>> >>>>>> There are no zombie processes. >>>>>> >>>>>> In mean time the problem shows on multiple servers and so far saw it >>>>>> only in cgroups that were OOMed. >>>>>> >>>>>> What has changed on these servers (yesterday) is turning on >>>>>> memory.oom.group=1 for all cgroups and changing memory.high from 1G to >>>>>> "max" (leaving memory.max=2G limit only). >>>>>> >>>>>> Previously there was no such problem. >>>>>> >>>>> >>>>> I'm attaching reproducer. This time tried on different distribution >>>>> kernel (arch linux). >>>>> >>>>> After 60s pids.current still shows 37 processes even if there are no >>>>> processes running (according to ps aux). >>>> >>>> >>>> The same test on 5.0.0-rc3-00104-gc04e2a780caf and it's easy to >>>> reproduce bug. No processes in cgroup but pids.current reports 91. >>> >>> Can you please see whether the problem can be reproduced on the >>> current linux-next? >>> >>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git >> >> I can reproduce on next (5.0.0-rc3-next-20190125), too: > > How reliably you can reproduce it? I've tried to run your reproducer > several times with different parameters, but wasn't lucky so far. Hmm, I'm able to reproduce each time using that python3 script. > What's yours cpu number and total ram size? On different machines: 1) old pc, 1 x intel E6600, 4GB of ram (arch linux 4.20.3 distro kernel), using python script 2) virtualbox vm, 1 cpu with 2 cores, 8GB of ram (pld kernel and custom built kernels like 5.0rc3 and 5.0rc3 next), using python script 3) server with 2 x intel E5405, 32GB of ram (4.19.13), with real life scenario 4) server with 1 x intel E5-2630 v2, 64GB of ram (4.19.15), with real life scenario > > Can you, please, provide the corresponding dmesg output? >From my virtualbox vm, after 60s pids.current reports 7 despite no processes: http://ixion.pld-linux.org/~arekm/cgroup-oom-1.txt kernel config: http://ixion.pld-linux.org/~arekm/cgroup-oom-kernelconf-1.txt Using 5.0.0-rc3-next-20190125 on that vm. > I've checked the code again, and my wild guess is that these missing > tasks are waiting (maybe hopelessly) for the OOM reaper. Dmesg output > might be very useful here. > > Thanks! > -- Arkadiusz Miśkiewicz, arekm / ( maven.pl | pld-linux.org )
