From: Vasily Averin <vvs@virtuozzo.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks
Date: Mon, 13 Sep 2021 13:35:00 +0300 [thread overview]
Message-ID: <7af26106-388c-6f99-e018-669a8f0cf9b5@virtuozzo.com> (raw)
In-Reply-To: <YT8RjxShvfEVe4YU@dhcp22.suse.cz>
On 9/13/21 11:53 AM, Michal Hocko wrote:
> On Fri 10-09-21 15:39:28, 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.
>> 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>
>> ---
>> mm/memcontrol.c | 23 +++++------------------
>> 1 file changed, 5 insertions(+), 18 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 389b5766e74f..67195fcfbddf 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -1834,6 +1834,9 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int
>> return OOM_ASYNC;
>> }
>>
>> + if (should_force_charge())
>> + return OOM_SKIPPED;
>
> mem_cgroup_out_of_memory already check for the bypass, now you are
> duplicating that check with a different answer to the caller. This is
> really messy. One of the two has to go away.
In this case mem_cgroup_out_of_memory() takes locks and mutexes but doing nothing
useful and its success causes try_charge_memcg() to repeat the loop unnecessarily.
I cannot change mem_cgroup_out_of_memory internals, because it is used in other places too.The check inside mem_cgroup_out_of_memory is required because situation can be changed after
check added into mem_cgroup_oom().
Though I got your argument, and will think how to improve the patch.
Anyway we'll need to do something with name of should_force_charge() function
that will NOT lead to forced charge.
Thank you,
Vasily Averin
Thank you,
next prev parent reply other threads:[~2021-09-13 10:35 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
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 [this message]
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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