On 2018-06-15, Aleksa Sarai <asarai@xxxxxxx> wrote: > > I've tested this on 4.14.27 and 4.4.0-124-generic Ubuntu. > > > > If I start a couple of processes which exit very quickly (like a simple Bash > > script with many commands in it), the reported value in "pids.current" is > > not updated immediately when processes exit. This leads to too many > > processes incorrectly accounted in "pids.current" which hits the "pids.max" > > prematurely. > > One possible reason for this might be related to zombie processes. > cgroup.procs doesn't include any zombie processes (tasks are removed > when they exit(2)), but the pids controller does track zombies (tasks > are removed when the 'struct task' is put'd). This could explain why > there's a discrepancy which clears itself up after a short period of > time -- though I am not sure that your reproducer will actually produce > zombies (I only took a quick look at it). Scratch that -- it can happen even without zombies. Basically it just depends on when the 'task struct' is freed (which could happen arbitrarily later than the process exit(2)-ed). -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH <https://www.cyphar.com/>
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