From: Suren Baghdasaryan <surenb@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>, Michal Hocko <mhocko@suse.com>,
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>,
Minchan Kim <minchan@kernel.org>,
Christian Brauner <christian@brauner.io>,
Christoph Hellwig <hch@infradead.org>,
Oleg Nesterov <oleg@redhat.com>,
David Hildenbrand <david@redhat.com>,
Jann Horn <jannh@google.com>, Shakeel Butt <shakeelb@google.com>,
Andy Lutomirski <luto@kernel.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
Florian Weimer <fweimer@redhat.com>,
Jan Engelhardt <jengelh@inai.de>,
Tim Murray <timmurray@google.com>,
Linux API <linux-api@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team <kernel-team@android.com>
Subject: Re: [PATCH v6 1/2] mm: introduce process_mrelease system call
Date: Wed, 4 Aug 2021 15:55:00 -0700 [thread overview]
Message-ID: <CAJuCfpHjvaOpUbg-UaZowgs0P-FN3P79VXnC-HuriK8SUqCX0g@mail.gmail.com> (raw)
In-Reply-To: <20210804155024.e4e42e1b7b087937271fa7ce@linux-foundation.org>
On Wed, Aug 4, 2021 at 3:50 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 4 Aug 2021 11:50:03 -0700 Suren Baghdasaryan <surenb@google.com> wrote:
>
> > In modern systems it's not unusual to have a system component monitoring
> > memory conditions of the system and tasked with keeping system memory
> > pressure under control. One way to accomplish that is to kill
> > non-essential processes to free up memory for more important ones.
> > Examples of this are Facebook's OOM killer daemon called oomd and
> > Android's low memory killer daemon called lmkd.
> > For such system component it's important to be able to free memory
> > quickly and efficiently. Unfortunately the time process takes to free
> > up its memory after receiving a SIGKILL might vary based on the state
> > of the process (uninterruptible sleep), size and OPP level of the core
> > the process is running. A mechanism to free resources of the target
> > process in a more predictable way would improve system's ability to
> > control its memory pressure.
> > Introduce process_mrelease system call that releases memory of a dying
> > process from the context of the caller. This way the memory is freed in
> > a more controllable way with CPU affinity and priority of the caller.
> > The workload of freeing the memory will also be charged to the caller.
> > The operation is allowed only on a dying process.
> >
> > After previous discussions [1, 2, 3] the decision was made [4] to introduce
> > a dedicated system call to cover this use case.
> >
> > The API is as follows,
> >
> > int process_mrelease(int pidfd, unsigned int flags);
> >
> > DESCRIPTION
> > The process_mrelease() system call is used to free the memory of
> > an exiting process.
> >
> > The pidfd selects the process referred to by the PID file
> > descriptor.
> > (See pidofd_open(2) for further information)
>
> I did s/pidofd_open/pidfd_open/
Thanks!
>
> >
> > The flags argument is reserved for future use; currently, this
> > argument must be specified as 0.
> >
> > RETURN VALUE
> > On success, process_mrelease() returns 0. On error, -1 is
> > returned and errno is set to indicate the error.
> >
> > ERRORS
> > EBADF pidfd is not a valid PID file descriptor.
> >
> > EAGAIN Failed to release part of the address space.
> >
> > EINTR The call was interrupted by a signal; see signal(7).
> >
> > EINVAL flags is not 0.
> >
> > EINVAL The memory of the task cannot be released because the
> > process is not exiting, the address space is shared
> > with another live process or there is a core dump in
> > progress.
> >
> > ENOSYS This system call is not supported, for example, without
> > MMU support built into Linux.
> >
> > ESRCH The target process does not exist (i.e., it has terminated
> > and been waited on).
> >
> > ...
> >
> > mm/oom_kill.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 65 insertions(+)
>
> The code is nice and simple.
>
> Can we get a test suite into tools/testing/selftests?
Let me take a stab at it.
Thanks!
next prev parent reply other threads:[~2021-08-04 22:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-04 18:50 [PATCH v6 1/2] mm: introduce process_mrelease system call Suren Baghdasaryan
2021-08-04 18:50 ` [PATCH v6 2/2] mm: wire up syscall process_mrelease Suren Baghdasaryan
2021-08-04 18:58 ` [PATCH v6 1/2] mm: introduce process_mrelease system call David Hildenbrand
2021-08-04 22:50 ` Andrew Morton
2021-08-04 22:55 ` Suren Baghdasaryan [this message]
2021-08-04 22:59 ` Shakeel Butt
2021-08-05 7:10 ` Michal Hocko
2021-08-05 15:29 ` Suren Baghdasaryan
2021-08-05 15:31 ` David Hildenbrand
2021-08-05 17:11 ` Suren Baghdasaryan
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