From: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Matthew Wilcox <willy@infradead.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>,
Christian Brauner <christian@brauner.io>,
Oleg Nesterov <oleg@redhat.com>,
Tim Murray <timmurray@google.com>,
linux-api@vger.kernel.org, linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team <kernel-team@android.com>,
Minchan Kim <minchan@kernel.org>
Subject: Re: [PATCH 1/1] RFC: add pidfd_send_signal flag to reclaim mm while killing a process
Date: Wed, 18 Nov 2020 11:55:31 -0800 [thread overview]
Message-ID: <CAJuCfpHP0n6Fyi6Lt9dUyYE72S5=iONkvDMkVSmKo6oRPjbMXQ@mail.gmail.com> (raw)
In-Reply-To: <CAJuCfpGucpqxOzGhteFrtv-0HrSbAmZjLbA2=NCy-5UEx04mJw@mail.gmail.com>
On Wed, Nov 18, 2020 at 11:51 AM Suren Baghdasaryan <surenb@google.com> wrote:
>
> On Wed, Nov 18, 2020 at 11:32 AM Michal Hocko <mhocko@suse.com> wrote:
> >
> > On Wed 18-11-20 11:22:21, Suren Baghdasaryan wrote:
> > > On Wed, Nov 18, 2020 at 11:10 AM Michal Hocko <mhocko@suse.com> wrote:
> > > >
> > > > On Fri 13-11-20 18:16:32, Andrew Morton wrote:
> > > > [...]
> > > > > It's all sounding a bit painful (but not *too* painful). But to
> > > > > reiterate, I do think that adding the ability for a process to shoot
> > > > > down a large amount of another process's memory is a lot more generally
> > > > > useful than tying it to SIGKILL, agree?
> > > >
> > > > I am not sure TBH. Is there any reasonable usecase where uncoordinated
> > > > memory tear down is OK and a target process which is able to see the
> > > > unmapped memory?
> > >
> > > I think uncoordinated memory tear down is a special case which makes
> > > sense only when the target process is being killed (and we can enforce
> > > that by allowing MADV_DONTNEED to be used only if the target process
> > > has pending SIGKILL).
> >
> > That would be safe but then I am wondering whether it makes sense to
> > implement as a madvise call. It is quite strange to expect somebody call
> > a syscall on a killed process. But this is more a detail. I am not a
> > great fan of a more generic MADV_DONTNEED on a remote process. This is
> > just too dangerous IMHO.
>
> Agree 100%
I assumed here that by "a more generic MADV_DONTNEED on a remote
process" you meant "process_madvise(MADV_DONTNEED) applied to a
process that is not being killed". Re-reading your comment I realized
that you might have meant "process_madvice() with generic support to
large memory areas". I hope I understood you correctly.
>
> >
> > > However, the ability to apply other flavors of
> > > process_madvise() to large memory areas spanning multiple VMAs can be
> > > useful in more cases.
> >
> > Yes I do agree with that. The error reporting would be more tricky but
> > I am not really sure that the exact reporting is really necessary for
> > advice like interface.
>
> Andrew's suggestion for this special mode to change return semantics
> to the usual "0 or error code" seems to me like the most reasonable
> way to deal with the return value limitation.
>
> >
> > > For example in Android we will use
> > > process_madvise(MADV_PAGEOUT) to "shrink" an inactive background
> > > process.
> >
> > That makes sense to me.
> > --
> > Michal Hocko
> > SUSE Labs
next prev parent reply other threads:[~2020-11-18 19:56 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-13 17:34 [PATCH 1/1] RFC: add pidfd_send_signal flag to reclaim mm while killing a process Suren Baghdasaryan
2020-11-13 23:55 ` Andrew Morton
2020-11-14 0:06 ` Suren Baghdasaryan
2020-11-14 1:00 ` Andrew Morton
2020-11-14 1:09 ` Suren Baghdasaryan
2020-11-14 1:18 ` Andrew Morton
2020-11-14 1:57 ` Suren Baghdasaryan
2020-11-14 2:16 ` Andrew Morton
2020-11-14 2:51 ` Suren Baghdasaryan
2020-11-16 23:24 ` Minchan Kim
2020-11-18 19:10 ` Michal Hocko
2020-11-18 19:22 ` Suren Baghdasaryan
2020-11-18 19:32 ` Michal Hocko
2020-11-18 19:51 ` Suren Baghdasaryan
2020-11-18 19:55 ` Suren Baghdasaryan [this message]
2020-11-19 0:13 ` Suren Baghdasaryan
2020-11-24 5:45 ` Suren Baghdasaryan
2020-11-18 10:32 ` Christian Brauner
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