From: Sultan Alsawaf <sultan@kerneltoast.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Mel Gorman <mgorman@suse.de>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: Mark the OOM reaper thread as freezable
Date: Mon, 20 Sep 2021 12:16:39 -0700 [thread overview]
Message-ID: <YUjeF6YsHKljSFis@sultan-box.localdomain> (raw)
In-Reply-To: <YUjGIuQciY7HNj+Y@dhcp22.suse.cz>
On Mon, Sep 20, 2021 at 07:34:26PM +0200, Michal Hocko wrote:
> The intention and the scope of the patch should be in the changelog.
> Your Fixes tag suggests there is a problem to fixed.
I guess References would be more appropriate here? I'm not familiar with every
subsystem's way of doing things, so I just rolled with Fixes to leave a
breadcrumb trail to the original commit implicated in my change. What would you
suggest in a case like this for mm patches?
> My memory has faded but I suspect it was to make sure that the oom
> reaper is not blocking the system wide freezing. The operation mode of
> the thread is to wait for oom victims and then do the unmapping without
> any blocking. While it can be frozen during the operation I do not
> remember that causing any problems and the waiting is exactly the point
> when that is obviously safe - hence wait_event_freezable which I believe
> is the proper API to use.
This isn't clear to me. Kthreads come with PF_NOFREEZE set by default, so the
system-wide freezing will already ignore the reaper thread as-is, although it
will make that determination from inside freeze_task() and thus
freezing_slow_path(), which involves acquiring a lock. You could set
PF_FREEZER_SKIP to skip the slowpath evaluation entirely.
Furthermore, the use of wait_event_freezable() will make the reaper thread enter
try_to_freeze() every time it's woken up. This seems wasteful considering that
the reaper thread will never actually freeze.
Sultan
next prev parent reply other threads:[~2021-09-20 19:18 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-18 23:39 [PATCH] mm: Mark the OOM reaper thread as freezable Sultan Alsawaf
2021-09-19 22:40 ` Andrew Morton
2021-09-20 12:40 ` Michal Hocko
2021-09-20 15:55 ` Sultan Alsawaf
2021-09-20 17:34 ` Michal Hocko
2021-09-20 19:16 ` Sultan Alsawaf [this message]
2021-09-20 20:30 ` Michal Hocko
2021-09-20 22:29 ` Sultan Alsawaf
2021-09-21 7:50 ` Michal Hocko
2021-09-21 10:48 ` Michal Hocko
2021-09-21 16:57 ` [PATCH v2] " Sultan Alsawaf
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=YUjeF6YsHKljSFis@sultan-box.localdomain \
--to=sultan@kerneltoast.com \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=mhocko@suse.com \
--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).