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Subject: Re: [PATCH memcg 1/3] mm: do not firce global OOM from inside dying
 tasks
To:     Michal Hocko <mhocko@suse.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <guro@fb.com>,
        Uladzislau Rezki <urezki@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Shakeel Butt <shakeelb@google.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        cgroups@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel@openvz.org
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From:   Vasily Averin <vvs@virtuozzo.com>
Message-ID: <f7329c84-3687-459e-88b6-c3395f538a0b@virtuozzo.com>
Date:   Wed, 20 Oct 2021 16:52:53 +0300
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On 20.10.2021 15:33, Michal Hocko wrote:
> s@firce@force@
> 
> On Wed 20-10-21 15:12:19, Vasily Averin wrote:
>> There is no sense to force global OOM if current task is dying.
> 
> This really begs for much more information. Feel free to get an
> inspiration from my previous attempt to achieve something similar.
> In minimum it is important to mention that the OOM killer is already
> handled at the page allocator level for the global OOM and at the
> charging level for the memcg one. Both have much more information
> about the scope of allocation/charge request. This means that either the
> OOM killer has been invoked properly and didn't lead to the allocation
> success or it has been skipped because it couldn't have been invoked.
> In both cases triggering it from here is pointless and even harmful.
> 
> Another argument is that it is more reasonable to let killed task die
> rather than hit the oom killer and retry the allocation.

Thank you,
I'll update  patch description later,
this time I would like to clarify patch content. 

>> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
>> ---
>>  mm/oom_kill.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
>> index 831340e7ad8b..1deef8c7a71b 100644
>> --- a/mm/oom_kill.c
>> +++ b/mm/oom_kill.c
>> @@ -1137,6 +1137,9 @@ void pagefault_out_of_memory(void)
>>  	if (mem_cgroup_oom_synchronize(true))
>>  		return;
>>  
>> +	if (fatal_signal_pending(current))
>> +		return;
>> +
>>  	if (!mutex_trylock(&oom_lock))
>>  		return;
>>  	out_of_memory(&oc);
>> -- 
>> 2.32.0
>