Re: [PATCH] ipc: remove memcg accounting for sops objects in do_semtimedop()
flat view
From: Michal Hocko <hidden>
Date: 2021-09-13 08:37:37
Also in:
lkml
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?
quoted hunk ↗ jump to hunk
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-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org/ Fixes: 18319498fdd4 ("memcg: enable accounting of ipc resources") Signed-off-by: Vasily Averin <redacted> --- 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