All of lore.kernel.org
 help / color / mirror / Atom feed
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>, Michal Hocko <mhocko@kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Michal Hocko <mhocko@suse.com>
Subject: Re: [RFC PATCH] mm: silence soft lockups from unlock_page
Date: Sat, 25 Jul 2020 11:48:41 -0700	[thread overview]
Message-ID: <CAHk-=whSJbODMVmxxDs64f7BaESKWuMqOxWGpjUSDn6Jzqa71g@mail.gmail.com> (raw)
In-Reply-To: <20200725101445.GB3870@redhat.com>

On Sat, Jul 25, 2020 at 3:14 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> Heh. I too thought about this. And just in case, your patch looks correct
> to me. But I can't really comment this behavioural change. Perhaps it
> should come in a separate patch?

We could do that. At the same time, I think both parts change how the
waitqueue works that it might as well just be one "fix page_bit_wait
waitqueue usage".

But let's wait to see what Hugh's numbers say.

> In essense, this partly reverts your commit 3510ca20ece0150
> ("Minor page waitqueue cleanups"). I mean this part:

Well, no. I mean, it keeps the "always add to the fail" behavior.

But some of the reasons for it have gone away. Now we could just make
it go back to always doing non-exclusive waits at the head.

The non-exclusive waiters _used_ to re-insert themselves on the queue
until they saw the bit clear, so waking them up if the bit was just
going to be set again was just going to make for unnecessary
scheduling and waitlist noise.

That reason is gone.

But I think the fundamental fairness issue might still be there. So
I'll keep the simpler "always add at the end".

But you're right - we could expedite the non-exclusive waiters even more.

             Linus

  reply	other threads:[~2020-07-25 18:49 UTC|newest]

Thread overview: 91+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-21  6:32 [RFC PATCH] mm: silence soft lockups from unlock_page Michal Hocko
2020-07-21 11:10 ` Qian Cai
2020-07-21 11:25   ` Michal Hocko
2020-07-21 11:44     ` Qian Cai
2020-07-21 12:17       ` Michal Hocko
2020-07-21 13:23         ` Qian Cai
2020-07-21 13:38           ` Michal Hocko
2020-07-21 14:15             ` Qian Cai
2020-07-21 14:17 ` Chris Down
2020-07-21 15:00   ` Michal Hocko
2020-07-21 15:33 ` Linus Torvalds
2020-07-21 15:33   ` Linus Torvalds
2020-07-21 15:49   ` Michal Hocko
2020-07-22 18:29   ` Linus Torvalds
2020-07-22 18:29     ` Linus Torvalds
2020-07-22 21:29     ` Hugh Dickins
2020-07-22 21:29       ` Hugh Dickins
2020-07-22 22:10       ` Linus Torvalds
2020-07-22 22:10         ` Linus Torvalds
2020-07-22 23:42         ` Linus Torvalds
2020-07-22 23:42           ` Linus Torvalds
2020-07-23  0:23           ` Linus Torvalds
2020-07-23  0:23             ` Linus Torvalds
2020-07-23 12:47           ` Oleg Nesterov
2020-07-23 17:32             ` Linus Torvalds
2020-07-23 17:32               ` Linus Torvalds
2020-07-23 18:01               ` Oleg Nesterov
2020-07-23 18:22                 ` Linus Torvalds
2020-07-23 18:22                   ` Linus Torvalds
2020-07-23 19:03                   ` Linus Torvalds
2020-07-23 19:03                     ` Linus Torvalds
2020-07-24 14:45                     ` Oleg Nesterov
2020-07-23 20:03               ` Linus Torvalds
2020-07-23 20:03                 ` Linus Torvalds
2020-07-23 23:11                 ` Hugh Dickins
2020-07-23 23:11                   ` Hugh Dickins
2020-07-23 23:43                   ` Linus Torvalds
2020-07-23 23:43                     ` Linus Torvalds
2020-07-24  0:07                     ` Hugh Dickins
2020-07-24  0:07                       ` Hugh Dickins
2020-07-24  0:46                       ` Linus Torvalds
2020-07-24  0:46                         ` Linus Torvalds
2020-07-24  3:45                         ` Hugh Dickins
2020-07-24  3:45                           ` Hugh Dickins
2020-07-24 15:24                     ` Oleg Nesterov
2020-07-24 17:32                       ` Linus Torvalds
2020-07-24 17:32                         ` Linus Torvalds
2020-07-24 23:25                         ` Linus Torvalds
2020-07-24 23:25                           ` Linus Torvalds
2020-07-25  2:08                           ` Hugh Dickins
2020-07-25  2:08                             ` Hugh Dickins
2020-07-25  2:46                             ` Linus Torvalds
2020-07-25  2:46                               ` Linus Torvalds
2020-07-25 10:14                           ` Oleg Nesterov
2020-07-25 18:48                             ` Linus Torvalds [this message]
2020-07-25 18:48                               ` Linus Torvalds
2020-07-25 19:27                               ` Oleg Nesterov
2020-07-25 19:51                                 ` Linus Torvalds
2020-07-25 19:51                                   ` Linus Torvalds
2020-07-26 13:57                                   ` Oleg Nesterov
2020-07-25 21:19                               ` Hugh Dickins
2020-07-25 21:19                                 ` Hugh Dickins
2020-07-26  4:22                                 ` Hugh Dickins
2020-07-26  4:22                                   ` Hugh Dickins
2020-07-26 20:30                                   ` Hugh Dickins
2020-07-26 20:30                                     ` Hugh Dickins
2020-07-26 20:41                                     ` Linus Torvalds
2020-07-26 20:41                                       ` Linus Torvalds
2020-07-26 22:09                                       ` Hugh Dickins
2020-07-26 22:09                                         ` Hugh Dickins
2020-07-27 19:35                                     ` Greg KH
2020-08-06  5:46                                       ` Hugh Dickins
2020-08-06  5:46                                         ` Hugh Dickins
2020-08-18 13:50                                         ` Greg KH
2020-08-06  5:21                                     ` Hugh Dickins
2020-08-06  5:21                                       ` Hugh Dickins
2020-08-06 17:07                                       ` Linus Torvalds
2020-08-06 17:07                                         ` Linus Torvalds
2020-08-06 18:00                                         ` Matthew Wilcox
2020-08-06 18:32                                           ` Linus Torvalds
2020-08-06 18:32                                             ` Linus Torvalds
2020-08-07 18:41                                             ` Hugh Dickins
2020-08-07 18:41                                               ` Hugh Dickins
2020-08-07 19:07                                               ` Linus Torvalds
2020-08-07 19:07                                                 ` Linus Torvalds
2020-08-07 19:35                                               ` Matthew Wilcox
2020-08-03 13:14                           ` Michal Hocko
2020-08-03 17:56                             ` Linus Torvalds
2020-08-03 17:56                               ` Linus Torvalds
2020-07-25  9:39                         ` Oleg Nesterov
2020-07-23  8:03     ` 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='CAHk-=whSJbODMVmxxDs64f7BaESKWuMqOxWGpjUSDn6Jzqa71g@mail.gmail.com' \
    --to=torvalds@linux-foundation.org \
    --cc=akpm@linux-foundation.org \
    --cc=hughd@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@kernel.org \
    --cc=mhocko@suse.com \
    --cc=oleg@redhat.com \
    --cc=tim.c.chen@linux.intel.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.