From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: linux-mm@kvack.org, hannes@cmpxchg.org, rientjes@google.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/page_alloc: Wait for oom_lock before retrying.
Date: Mon, 17 Jul 2017 10:56:05 +0200 [thread overview]
Message-ID: <20170717085605.GE12888@dhcp22.suse.cz> (raw)
In-Reply-To: <1500202791-5427-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
On Sun 16-07-17 19:59:51, Tetsuo Handa wrote:
> Since the whole memory reclaim path has never been designed to handle the
> scheduling priority inversions, those locations which are assuming that
> execution of some code path shall eventually complete without using
> synchronization mechanisms can get stuck (livelock) due to scheduling
> priority inversions, for CPU time is not guaranteed to be yielded to some
> thread doing such code path.
>
> mutex_trylock() in __alloc_pages_may_oom() (waiting for oom_lock) and
> schedule_timeout_killable(1) in out_of_memory() (already held oom_lock) is
> one of such locations, and it was demonstrated using artificial stressing
> that the system gets stuck effectively forever because SCHED_IDLE priority
> thread is unable to resume execution at schedule_timeout_killable(1) if
> a lot of !SCHED_IDLE priority threads are wasting CPU time [1].
I do not understand this. All the contending tasks will go and sleep for
1s. How can they preempt the lock holder?
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-07-17 8:56 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-16 10:59 [PATCH v2] mm/page_alloc: Wait for oom_lock before retrying Tetsuo Handa
2017-07-17 8:56 ` Michal Hocko [this message]
2017-07-17 13:50 ` Tetsuo Handa
2017-07-17 15:15 ` Michal Hocko
2017-07-17 15:24 ` Michal Hocko
2017-07-17 21:42 ` Tetsuo Handa
2017-07-18 9:08 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170717085605.GE12888@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=rientjes@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).