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, kernel@openvz.org
Subject: Re: [PATCH mm] vmalloc: back off when the current task is OOM-killed
Date: Mon, 27 Sep 2021 12:36:15 +0300 [thread overview]
Message-ID: <508abe37-a044-7180-ac67-b4ce5e4cc149@virtuozzo.com> (raw)
In-Reply-To: <YU2EXP5wrSKv+b/8@dhcp22.suse.cz>
On 9/24/21 10:55 AM, Michal Hocko wrote:
> On Thu 23-09-21 09:49:57, Vasily Averin wrote:
> [...]
>> I'm agree that vmalloc callers should expect and handle single vnalloc failures.
>> I think it is acceptable to enable fatal_signal_pending check to quickly
>> detect such kind of iussues.
>> However fatal_signal_pending check can cause serial vmalloc failures
>> and I doubt it is acceptable.
>>
>> Rollback after failed vmalloc can call new vmalloc calls that will be failed too,
>> even properly handled such serial failures can cause troubles.
>
> Could you be more specific? Also how would this be any different from
> similar failures for an oom victim? Except that the later is less likely
> so (as already mentioend) any potential bugs would be just lurking there
> for a longer time.
>
>> Hypothetically, cancelled vmalloc called inside some filesystem's transaction
>> forces its rollback, that in own turn it can call own vmalloc.
>
> Do you have any specific example?
No, it was pure hypothetical assumption.
I was thinking about it over the weekend, and decided that:
a) such kind of issue (i.e. vmalloc call in rollback after failed vmalloc)
is very unlikely
b) if it still exists -- it must have own failback with kmalloc(NOFAIL)
or just accept/ignore such failure and should not lead to critical failures.
If this still happen -- ihis is a bug, we should detect and fix it ASAP.
>> Should we perhaps interrupt the first vmalloc only?
>
> This doesn't make much sense to me TBH. It doesn't address the very
> problem you are describing in the changelog.
Last question:
how do you think, should we perhaps, instead, detect such vmallocs
(called in rollback after failed vmalloc) and generate a warnings,
to prevent such kind of problems in future?
Thank you,
Vasily Averin
next prev parent reply other threads:[~2021-09-27 9:36 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 [this message]
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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