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Re: can't oom-kill zap the victim's memory?

From Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Newsgroups linux.kernel
Subject Re: can't oom-kill zap the victim's memory?
Date 2015-09-20 17:00 +0200
Message-ID <qaOfT-2Yb-1@gated-at.bofh.it> (permalink)
References <q9LN8-2Wt-13@gated-at.bofh.it> <qarW1-4WN-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Oleg Nesterov wrote:
> On 09/17, Kyle Walker wrote:
> >
> > Currently, the oom killer will attempt to kill a process that is in
> > TASK_UNINTERRUPTIBLE state. For tasks in this state for an exceptional
> > period of time, such as processes writing to a frozen filesystem during
> > a lengthy backup operation, this can result in a deadlock condition as
> > related processes memory access will stall within the page fault
> > handler.
> 
> And there are other potential reasons for deadlock.
> 
> Stupid idea. Can't we help the memory hog to free its memory? This is
> orthogonal to other improvements we can do.

So, we are trying to release memory without waiting for arriving at
exit_mm() from do_exit(), right? If it works, it will be a simple and
small change that will be easy to backport.

The idea is that since fatal_signal_pending() tasks no longer return to
user space, we can release memory allocated for use by user space, right?

Then, I think that this approach can be applied to not only OOM-kill case
but also regular kill(pid, SIGKILL) case (i.e. kick from signal_wake_up(1)
or somewhere?). A dedicated kernel thread (not limited to OOM-kill purpose)
scans for fatal_signal_pending() tasks and release that task's memory.
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Thread

[PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Kyle Walker <kwalker@redhat.com> - 2015-09-17 20:10 +0200
  Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-17 21:30 +0200
    Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-18 17:50 +0200
      Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-18 18:30 +0200
        Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-18 18:50 +0200
          Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-18 19:00 +0200
        Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-18 19:10 +0200
          Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-18 21:20 +0200
            Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-18 21:20 +0200
              Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Christoph Lameter <cl@linux.com> - 2015-09-19 00:10 +0200
          Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 10:40 +0200
            Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-19 16:40 +0200
              Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 18:00 +0200
              Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks David Rientjes <rientjes@google.com> - 2015-09-22 01:40 +0200
                Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-22 07:40 +0200
            Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Oleg Nesterov <oleg@redhat.com> - 2015-09-19 16:50 +0200
          Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks David Rientjes <rientjes@google.com> - 2015-09-22 01:30 +0200
      Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 10:30 +0200
  Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks Michal Hocko <mhocko@kernel.org> - 2015-09-19 10:30 +0200
    Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks David Rientjes <rientjes@google.com> - 2015-09-22 01:10 +0200
  can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-19 17:10 +0200
    Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-19 17:20 +0200
    Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-19 18:00 +0200
      Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 15:20 +0200
    Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-20 00:30 +0200
      Re: can't oom-kill zap the victim's memory? Raymond Jennings <shentino@gmail.com> - 2015-09-20 01:10 +0200
        Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-20 01:20 +0200
      Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-20 11:40 +0200
        Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 15:10 +0200
      Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 15:10 +0200
        Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-20 20:10 +0200
          Re: can't oom-kill zap the victim's memory? Raymond Jennings <shentino@gmail.com> - 2015-09-20 21:10 +0200
            Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-21 16:10 +0200
          Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-21 15:50 +0200
            Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-21 16:30 +0200
              Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-21 17:40 +0200
                Re: can't oom-kill zap the victim's memory? Michal Hocko <mhocko@kernel.org> - 2015-09-21 18:20 +0200
                Re: can't oom-kill zap the victim's memory? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-21 19:00 +0200
                Re: can't oom-kill zap the victim's memory? David Rientjes <rientjes@google.com> - 2015-09-22 01:50 +0200
            Re: can't oom-kill zap the victim's memory? Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-21 19:00 +0200
    Re: can't oom-kill zap the victim's memory? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2015-09-20 17:00 +0200
      Re: can't oom-kill zap the victim's memory? Oleg Nesterov <oleg@redhat.com> - 2015-09-20 17:00 +0200

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