From: Andrew Morton <akpm@linux-foundation.org>
To: Suren Baghdasaryan <surenb@google.com>
Cc: mhocko@kernel.org, mhocko@suse.com, rientjes@google.com,
willy@infradead.org, hannes@cmpxchg.org, guro@fb.com,
riel@surriel.com, minchan@kernel.org, christian@brauner.io,
hch@infradead.org, oleg@redhat.com, david@redhat.com,
jannh@google.com, shakeelb@google.com, luto@kernel.org,
christian.brauner@ubuntu.com, fweimer@redhat.com,
jengelh@inai.de, timmurray@google.com, linux-api@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@android.com
Subject: Re: [PATCH v6 1/2] mm: introduce process_mrelease system call
Date: Wed, 4 Aug 2021 15:50:24 -0700 [thread overview]
Message-ID: <20210804155024.e4e42e1b7b087937271fa7ce@linux-foundation.org> (raw)
In-Reply-To: <20210804185004.1304692-1-surenb@google.com>
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/
>
> 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?
next prev parent reply other threads:[~2021-08-04 22:50 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 [this message]
2021-08-04 22:55 ` Suren Baghdasaryan
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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