From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Shakeel Butt <shakeelb@google.com>, Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Cgroups <cgroups@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes
Date: Mon, 15 Jan 2018 15:29:21 +0300 [thread overview]
Message-ID: <e5e92227-0931-dfc1-841e-c036131e66a8@virtuozzo.com> (raw)
In-Reply-To: <CALvZod6y8EfQt02+rNOP_JXgzpJJHjuVzd++T3E=NEMwwBv_CQ@mail.gmail.com>
On 01/13/2018 01:57 AM, Shakeel Butt wrote:
> On Fri, Jan 12, 2018 at 4:24 AM, Michal Hocko <mhocko@kernel.org> wrote:
>> On Fri 12-01-18 00:59:38, Andrey Ryabinin wrote:
>>> On 01/11/2018 07:29 PM, Michal Hocko wrote:
>> [...]
>>>> I do not think so. Consider that this reclaim races with other
>>>> reclaimers. Now you are reclaiming a large chunk so you might end up
>>>> reclaiming more than necessary. SWAP_CLUSTER_MAX would reduce the over
>>>> reclaim to be negligible.
>>>>
>>>
>>> I did consider this. And I think, I already explained that sort of race in previous email.
>>> Whether "Task B" is really a task in cgroup or it's actually a bunch of reclaimers,
>>> doesn't matter. That doesn't change anything.
>>
>> I would _really_ prefer two patches here. The first one removing the
>> hard coded reclaim count. That thing is just dubious at best. If you
>> _really_ think that the higher reclaim target is meaningfull then make
>> it a separate patch. I am not conviced but I will not nack it it either.
>> But it will make our life much easier if my over reclaim concern is
>> right and we will need to revert it. Conceptually those two changes are
>> independent anywa.
>>
>
> Personally I feel that the cgroup-v2 semantics are much cleaner for
> setting limit. There is no race with the allocators in the memcg,
> though oom-killer can be triggered. For cgroup-v1, the user does not
> expect OOM killer and EBUSY is expected on unsuccessful reclaim. How
> about we do something similar here and make sure oom killer can not be
> triggered for the given memcg?
>
> // pseudo code
> disable_oom(memcg)
> old = xchg(&memcg->memory.limit, requested_limit)
>
> reclaim memory until usage gets below new limit or retries are exhausted
>
> if (unsuccessful) {
> reset_limit(memcg, old)
> ret = EBUSY
> } else
> ret = 0;
> enable_oom(memcg)
>
> This way there is no race with the allocators and oom killer will not
> be triggered. The processes in the memcg can suffer but that should be
> within the expectation of the user. One disclaimer though, disabling
> oom for memcg needs more thought.
That's might be worse. If limit is too low, all allocations (except __GFP_NOFAIL of course) will start
failing. And the kernel not always careful enough in -ENOMEM handling.
Also, it's not much different from oom killing everything, the end result is almost the same -
nothing will work in that cgroup.
> Shakeel
>
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next prev parent reply other threads:[~2018-01-15 12:29 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-20 10:24 [PATCH 1/2] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Andrey Ryabinin
2017-12-20 10:24 ` [PATCH 2/2] mm/memcg: Consolidate mem_cgroup_resize_[memsw]_limit() functions Andrey Ryabinin
2017-12-20 10:33 ` [PATCH 1/2] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Michal Hocko
2017-12-20 11:32 ` Andrey Ryabinin
2017-12-20 11:34 ` Michal Hocko
2017-12-20 18:15 ` Shakeel Butt
2017-12-21 10:00 ` Andrey Ryabinin
2017-12-20 13:21 ` [PATCH v2 " Andrey Ryabinin
2017-12-20 13:21 ` [PATCH v2 2/2] mm/memcg: Consolidate mem_cgroup_resize_[memsw]_limit() functions Andrey Ryabinin
2017-12-20 13:53 ` [PATCH v2 1/2] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Michal Hocko
2018-01-09 16:58 ` [PATCH v3 " Andrey Ryabinin
2018-01-09 16:58 ` [PATCH v3 2/2] mm/memcg: Consolidate mem_cgroup_resize_[memsw]_limit() functions Andrey Ryabinin
2018-01-09 17:10 ` Shakeel Butt
2018-01-09 17:26 ` Andrey Ryabinin
2018-01-09 23:26 ` Andrew Morton
2018-01-10 12:43 ` [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Andrey Ryabinin
2018-01-10 22:31 ` Andrew Morton
2018-01-11 11:59 ` Andrey Ryabinin
2018-01-12 0:21 ` Andrew Morton
2018-01-12 9:08 ` Andrey Ryabinin
2018-01-11 10:42 ` Michal Hocko
2018-01-11 12:21 ` Andrey Ryabinin
2018-01-11 12:46 ` Michal Hocko
2018-01-11 15:23 ` Andrey Ryabinin
2018-01-11 16:29 ` Michal Hocko
2018-01-11 21:59 ` Andrey Ryabinin
2018-01-12 12:24 ` Michal Hocko
2018-01-12 22:57 ` Shakeel Butt
2018-01-15 12:29 ` Andrey Ryabinin [this message]
2018-01-15 17:04 ` Shakeel Butt
2018-01-15 12:30 ` Andrey Ryabinin
2018-01-15 12:46 ` Michal Hocko
2018-01-15 12:53 ` Andrey Ryabinin
2018-01-15 12:58 ` Michal Hocko
2018-01-09 17:08 ` [PATCH v3 1/2] " Andrey Ryabinin
2018-01-09 17:22 ` Shakeel Butt
2018-01-19 13:25 ` [PATCH v5 1/2] mm/memcontrol.c: " Andrey Ryabinin
2018-01-19 13:25 ` [PATCH v5 2/2] mm/memcontrol.c: Reduce reclaim retries in mem_cgroup_resize_limit() Andrey Ryabinin
2018-01-19 13:35 ` Michal Hocko
2018-01-19 14:49 ` Shakeel Butt
2018-01-19 15:11 ` Michal Hocko
2018-01-19 15:24 ` Shakeel Butt
2018-01-19 15:31 ` Michal Hocko
2018-02-21 20:17 ` Andrew Morton
2018-02-22 13:50 ` Andrey Ryabinin
2018-02-22 14:09 ` Michal Hocko
2018-02-22 15:13 ` Andrey Ryabinin
2018-02-22 15:33 ` Michal Hocko
2018-02-22 15:38 ` Andrey Ryabinin
2018-02-22 15:44 ` Michal Hocko
2018-02-22 16:01 ` Andrey Ryabinin
2018-02-22 16:30 ` Michal Hocko
2018-01-19 13:32 ` [PATCH v5 1/2] mm/memcontrol.c: try harder to decrease [memory,memsw].limit_in_bytes Michal Hocko
2018-01-25 19:44 ` Andrey Ryabinin
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