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From: Vasily Averin <vvs@virtuozzo.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: cgroups@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Michal Hocko <mhocko@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks
Date: Fri, 10 Sep 2021 16:20:58 +0300	[thread overview]
Message-ID: <4a407474-ff7a-9e4f-d314-ab85f0eeaadf@virtuozzo.com> (raw)
In-Reply-To: <099aa0db-045a-e5b8-6df7-b7c3fc4d3caa@i-love.sakura.ne.jp>

On 9/10/21 4:04 PM, Tetsuo Handa wrote:
> On 2021/09/10 21:39, Vasily Averin wrote:
>> The kernel currently allows dying tasks to exceed the memcg limits.
>> The allocation is expected to be the last one and the occupied memory
>> will be freed soon.
>> This is not always true because it can be part of the huge vmalloc
>> allocation. Allowed once, they will repeat over and over again.
>> Moreover lifetime of the allocated object can differ from
>> In addition the lifetime of the dying task.
> 
> Can't we add fatal_signal_pending(current) test to vmalloc() loop?

1) this has been done in the past but has been reverted later.
2) any vmalloc changes will affect non-memcg allocations too.
 If we're doing memcg-related checks it's better to do it in one place.
3) it is not vmalloc-only issue. Huge number of  kmalloc page allocations 
from N concurrent threads will lead to the same problem. 

>> Multiple such allocations running concurrently can not only overuse
>> the memcg limit, but can lead to a global out of memory and,
>> in the worst case, cause the host to panic.
>>
>> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>



  reply	other threads:[~2021-09-10 13:21 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-10 12:39 [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks Vasily Averin
2021-09-10 13:04 ` Tetsuo Handa
2021-09-10 13:20   ` Vasily Averin [this message]
2021-09-10 14:55     ` Michal Hocko
2021-09-13  8:29       ` Vasily Averin
2021-09-13  8:42         ` Michal Hocko
2021-09-17  8:06           ` [PATCH mm] vmalloc: back off when the current task is OOM-killed Vasily Averin
2021-09-19 23:31             ` Andrew Morton
2021-09-20  1:22               ` Tetsuo Handa
2021-09-20 10:59                 ` Vasily Averin
2021-09-21 18:55                   ` Andrew Morton
2021-09-22  6:18                     ` Vasily Averin
2021-09-22 12:27             ` Michal Hocko
2021-09-23  6:49               ` Vasily Averin
2021-09-24  7:55                 ` Michal Hocko
2021-09-27  9:36                   ` Vasily Averin
2021-09-27 11:08                     ` Michal Hocko
2021-10-05 13:52                       ` [PATCH mm v2] " Vasily Averin
2021-10-05 14:00                         ` Vasily Averin
2021-10-07 10:47                         ` Michal Hocko
2021-10-07 19:55                         ` Andrew Morton
2021-09-10 13:07 ` [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks Vasily Averin
2021-09-13  7:51 ` Vasily Averin
2021-09-13  8:39   ` Michal Hocko
2021-09-13  9:37     ` Vasily Averin
2021-09-13 10:10       ` Michal Hocko
2021-09-13  8:53 ` Michal Hocko
2021-09-13 10:35   ` Vasily Averin
2021-09-13 10:55     ` Michal Hocko
2021-09-14 10:01       ` Vasily Averin
2021-09-14 10:10         ` [PATCH memcg v2] " Vasily Averin
2021-09-16 12:55           ` Michal Hocko
2021-10-05 13:52             ` [PATCH memcg v3] " Vasily Averin
2021-10-05 14:55               ` Michal Hocko

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