From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks Date: Mon, 13 Sep 2021 10:39:42 +0200 Message-ID: References: <5b06a490-55bc-a6a0-6c85-690254f86fad@virtuozzo.com> <8b98d44a-aeb2-5f5f-2545-ac2bd0c7049b@virtuozzo.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1631522383; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=YNVmy9/9lqHYvf3OJkSwSJB1fHLiXXPQ7bI/XZDPCbw=; b=c1HHg8ePrZfYQ80ef9MjqdceMy0V9FYZoCaBtu/1B1AwAORvSyJTM3OD3cRRQ/4fEkyTCa jZFgwaxgR3QJbaOsKHHrUCUfsTd436BsaRQWHlzlEKLzx6jRp1r2259heXsZgH8pGqUCGn BmY5q6RQIUfMQuRWPsw/GSgUu4/+T2w= Content-Disposition: inline In-Reply-To: <8b98d44a-aeb2-5f5f-2545-ac2bd0c7049b-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Vasily Averin Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Tetsuo Handa , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Mon 13-09-21 10:51:37, Vasily Averin wrote: > On 9/10/21 3:39 PM, Vasily Averin wrote: > > The kernel currently allows dying tasks to exceed the memcg limits. > > The allocation is expected to be the last one and the occupied memory > > will be freed soon. > > This is not always true because it can be part of the huge vmalloc > > allocation. Allowed once, they will repeat over and over again. > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 389b5766e74f..67195fcfbddf 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2622,15 +2625,6 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > > if (gfp_mask & __GFP_ATOMIC) > > goto force; > > > > - /* > > - * Unlike in global OOM situations, memcg is not in a physical > > - * memory shortage. Allow dying and OOM-killed tasks to > > - * bypass the last charges so that they can exit quickly and > > - * free their memory. > > - */ > > - if (unlikely(should_force_charge())) > > - goto force; > > - > > Should we keep current behaviour for (current->flags & PF_EXITING) case perhaps? Why? > It is set inside do_exit only and (I hope) cannot trigger huge vmalloc allocations. Allocations in this code path should be rare but it is not like they are non-existent. This is rather hard to review area spread at many places so if we are deciding to make the existing model simpler (no bypassing) then I would rather have no exceptions unless they are reaaly necessary and document them if they are. -- Michal Hocko SUSE Labs