Messages in this thread | | | Subject | Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task | From | Vasily Averin <> | Date | Tue, 19 Oct 2021 13:30:06 +0300 |
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On 19.10.2021 11:49, Michal Hocko wrote: > On Tue 19-10-21 09:30:18, Vasily Averin wrote: > [...] >> With my patch ("memcg: prohibit unconditional exceeding the limit of dying tasks") try_charge_memcg() can fail: >> a) due to fatal signal >> b) when mem_cgroup_oom -> mem_cgroup_out_of_memory -> out_of_memory() returns false (when select_bad_process() found nothing) >> >> To handle a) we can follow to your suggestion and skip excution of out_of_memory() in pagefault_out_of memory() >> To handle b) we can go to retry: if mem_cgroup_oom() return OOM_FAILED.
> How is b) possible without current being killed? Do we allow remote > charging?
out_of_memory for memcg_oom select_bad_process mem_cgroup_scan_tasks oom_evaluate_task oom_badness
/* * Do not even consider tasks which are explicitly marked oom * unkillable or have been already oom reaped or the are in * the middle of vfork */ adj = (long)p->signal->oom_score_adj; if (adj == OOM_SCORE_ADJ_MIN || test_bit(MMF_OOM_SKIP, &p->mm->flags) || in_vfork(p)) { task_unlock(p); return LONG_MIN; }
This time we handle userspace page fault, so we cannot be kenrel thread, and cannot be in_vfork(). However task can be marked as oom unkillable, i.e. have p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN
It can be set via oom_score_adj_write().
Thank you, Vasily Averin
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