linux-kernel - Re: [PATCH] mm/oom_kill: count global and memory cgroup oom kills

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Date:   Thu, 25 May 2017 11:44:41 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Roman Guschin <guroan@...il.com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>, hannes@...xchg.org
Subject: Re: [PATCH] mm/oom_kill: count global and memory cgroup oom kills



On 24.05.2017 23:43, David Rientjes wrote:
> On Tue, 23 May 2017, Konstantin Khlebnikov wrote:
> 
>> This is worth addition. Let's call it "oom_victim" for short.
>>
>> It allows to locate leaky part if they are spread over sub-containers within
>> common limit.
>> But doesn't tell which limit caused this kill. For hierarchical limits this
>> might be not so easy.
>>
>> I think oom_kill better suits for automatic actions - restart affected
>> hierarchy, increase limits, e.t.c.
>> But oom_victim allows to determine container affected by global oom killer.
>>
>> So, probably it's worth to merge them together and increment oom_kill by
>> global killer for victim memcg:
>>
>> 	if (!is_memcg_oom(oc)) {
>> 		count_vm_event(OOM_KILL);
>> 		mem_cgroup_count_vm_event(mm, OOM_KILL);
>> 	} else
>> 		mem_cgroup_event(oc->memcg, OOM_KILL);
>>
> 
> Our complete solution is that we have a complementary
> memory.oom_kill_control that allows users to register for eventfd(2)
> notification when the kernel oom killer kills a victim, but this is
> because we have had complete support for userspace oom handling for years.
> When read, it exports three classes of information:
> 
>   - the "total" (hierarchical) and "local" (memcg specific) number of oom
>     kills for system oom conditions (overcommit),
> 
>   - the "total" and "local" number of oom kills for memcg oom conditions,
>     and
>   
>   - the total number of processes in the hierarchy where an oom victim was
>     reaped successfully and unsuccessfully.
> 
> One benefit of this is that it prevents us from having to scrape the
> kernel log for oom events which has been troublesome in the past, but
> userspace can easily do so when the eventfd triggers for the kill
> notification.
> 

Ok. I've decided to simplify this thing and count kills to cgroup where task lived.
Like page faults. And show in vmstat total count of any kind of kills.

Simply:
	count_vm_event(OOM_KILL);
	mem_cgroup_count_vm_event(mm, OOM_KILL);