From: Daniel Colascione <dancol@google.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>,
Suren Baghdasaryan <surenb@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
yuzhoujian@didichuxing.com,
Souptick Joarder <jrdr.linux@gmail.com>,
Roman Gushchin <guro@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Shakeel Butt <shakeelb@google.com>,
Christian Brauner <christian@brauner.io>,
Minchan Kim <minchan@kernel.org>,
Tim Murray <timmurray@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
Jann Horn <jannh@google.com>, linux-mm <linux-mm@kvack.org>,
lsf-pc@lists.linux-foundation.org,
linux-kernel <linux-kernel@vger.kernel.org>,
Android Kernel Team <kernel-team@android.com>
Subject: Re: [RFC 2/2] signal: extend pidfd_send_signal() to allow expedited process killing
Date: Fri, 12 Apr 2019 07:14:30 -0700 [thread overview]
Message-ID: <CAKOZuetQH1rVtPdMNgw0sdnzWidd6v9eCWscRiOb7Y+3-JQ14Q@mail.gmail.com> (raw)
In-Reply-To: <20190412065314.GC13373@dhcp22.suse.cz>
On Thu, Apr 11, 2019 at 11:53 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Thu 11-04-19 08:33:13, Matthew Wilcox wrote:
> > On Wed, Apr 10, 2019 at 06:43:53PM -0700, Suren Baghdasaryan wrote:
> > > Add new SS_EXPEDITE flag to be used when sending SIGKILL via
> > > pidfd_send_signal() syscall to allow expedited memory reclaim of the
> > > victim process. The usage of this flag is currently limited to SIGKILL
> > > signal and only to privileged users.
> >
> > What is the downside of doing expedited memory reclaim? ie why not do it
> > every time a process is going to die?
>
> Well, you are tearing down an address space which might be still in use
> because the task not fully dead yeat. So there are two downsides AFAICS.
> Core dumping which will not see the reaped memory so the resulting
Test for SIGNAL_GROUP_COREDUMP before doing any of this then. If you
try to start a core dump after reaping begins, too bad: you could have
raced with process death anyway.
> coredump might be incomplete. And unexpected #PF/gup on the reaped
> memory will result in SIGBUS.
It's a dying process. Why even bother returning from the fault
handler? Just treat that situation as a thread exit. There's no need
to make this observable to userspace at all.
next prev parent reply other threads:[~2019-04-12 14:14 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-11 1:43 [RFC 0/2] opportunistic memory reclaim of a killed process Suren Baghdasaryan
2019-04-11 1:43 ` [RFC 1/2] mm: oom: expose expedite_reclaim to use oom_reaper outside of oom_kill.c Suren Baghdasaryan
2019-04-25 21:12 ` Tetsuo Handa
2019-04-25 21:56 ` Suren Baghdasaryan
2019-04-11 1:43 ` [RFC 2/2] signal: extend pidfd_send_signal() to allow expedited process killing Suren Baghdasaryan
2019-04-11 10:30 ` Christian Brauner
2019-04-11 10:34 ` Christian Brauner
2019-04-11 15:18 ` Suren Baghdasaryan
2019-04-11 15:23 ` Suren Baghdasaryan
2019-04-11 16:25 ` Daniel Colascione
2019-04-11 15:33 ` Matthew Wilcox
2019-04-11 17:05 ` Johannes Weiner
2019-04-11 17:09 ` Suren Baghdasaryan
2019-04-11 17:33 ` Daniel Colascione
2019-04-11 17:36 ` Matthew Wilcox
2019-04-11 17:47 ` Daniel Colascione
2019-04-12 6:49 ` Michal Hocko
2019-04-12 14:15 ` Suren Baghdasaryan
2019-04-12 14:20 ` Daniel Colascione
2019-04-12 21:03 ` Matthew Wilcox
2019-04-11 17:52 ` Suren Baghdasaryan
2019-04-11 21:45 ` Roman Gushchin
2019-04-11 21:59 ` Suren Baghdasaryan
2019-04-12 6:53 ` Michal Hocko
2019-04-12 14:10 ` Suren Baghdasaryan
2019-04-12 14:14 ` Daniel Colascione [this message]
2019-04-12 15:30 ` Daniel Colascione
2019-04-25 16:09 ` Suren Baghdasaryan
2019-04-11 10:51 ` [RFC 0/2] opportunistic memory reclaim of a killed process Michal Hocko
2019-04-11 16:18 ` Joel Fernandes
2019-04-11 18:12 ` Michal Hocko
2019-04-11 19:14 ` Joel Fernandes
2019-04-11 20:11 ` Michal Hocko
2019-04-11 21:11 ` Joel Fernandes
2019-04-11 16:20 ` Sandeep Patil
2019-04-11 16:47 ` Suren Baghdasaryan
2019-04-11 18:19 ` Michal Hocko
2019-04-11 19:56 ` Suren Baghdasaryan
2019-04-11 20:17 ` Michal Hocko
2019-04-11 17:19 ` Johannes Weiner
2019-04-11 11:51 ` [Lsf-pc] " Rik van Riel
2019-04-11 12:16 ` Michal Hocko
2019-04-11 16:54 ` Suren Baghdasaryan
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