From: Michal Hocko <mhocko@suse.com>
To: Vasily Averin <vvs@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Shakeel Butt <shakeelb@google.com>,
linux-kernel@vger.kernel.org,
Johannes Weiner <hannes@cmpxchg.org>,
kernel@openvz.org, cgroups@vger.kernel.org
Subject: Re: [PATCH] ipc: remove memcg accounting for sops objects in do_semtimedop()
Date: Mon, 13 Sep 2021 10:37:02 +0200 [thread overview]
Message-ID: <YT8NrsaztWNDpKXk@dhcp22.suse.cz> (raw)
In-Reply-To: <90e254df-0dfe-f080-011e-b7c53ee7fd20@virtuozzo.com>
On Sat 11-09-21 10:40:08, Vasily Averin wrote:
> Linus proposes to revert an accounting for sops objects in
> do_semtimedop() because it's really just a temporary buffer
> for a single semtimedop() system call.
>
> This object can consume up to 2 pages, syscall is sleeping one,
> size and duration can be controlled by user, and this allocation
> can be repeated by many thread at the same time.
Is there any upper bound or is it just bounded by the number of
tasks/threads (that can be controlled by pid controller at least)?
> However Shakeel Butt pointed that there are much more popular objects
> with the same life time and similar memory consumption, the accounting
> of which was decided to be rejected for performance reasons.
Is there any measurable performance impact in this particular case?
> In addition, any usual task consumes much more accounted memory,
> so 2 pages of this temporal buffer can be safely ignored.
>
> Link: https://patchwork.kernel.org/project/linux-fsdevel/patch/20171005222144.123797-1-shakeelb@google.com/
>
> Fixes: 18319498fdd4 ("memcg: enable accounting of ipc resources")
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
> ---
> ipc/sem.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/ipc/sem.c b/ipc/sem.c
> index f833238df1ce..6693daf4fe11 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -2238,7 +2238,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
> return -EINVAL;
>
> if (nsops > SEMOPM_FAST) {
> - sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL_ACCOUNT);
> + sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
> if (sops == NULL)
> return -ENOMEM;
> }
> --
> 2.25.1
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-09-13 8:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-11 7:40 [PATCH] ipc: remove memcg accounting for sops objects in do_semtimedop() Vasily Averin
2021-09-12 16:05 ` Shakeel Butt
2021-09-13 8:37 ` Michal Hocko [this message]
2021-09-14 4:32 ` Shakeel Butt
2021-09-14 7:13 ` Michal Hocko
2021-09-14 14:23 ` Michal Koutný
2021-09-14 14:32 ` Michal Hocko
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