From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B50CEC433F5 for ; Mon, 13 Sep 2021 08:39:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9231F60FBF for ; Mon, 13 Sep 2021 08:39:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238124AbhIMIlC (ORCPT ); Mon, 13 Sep 2021 04:41:02 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:49318 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237999AbhIMIk7 (ORCPT ); Mon, 13 Sep 2021 04:40:59 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 3FCA41FFAA; Mon, 13 Sep 2021 08:39:43 +0000 (UTC) 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= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id B4E89A3B81; Mon, 13 Sep 2021 08:39:42 +0000 (UTC) Date: Mon, 13 Sep 2021 10:39:42 +0200 From: Michal Hocko To: Vasily Averin Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Tetsuo Handa , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks Message-ID: References: <5b06a490-55bc-a6a0-6c85-690254f86fad@virtuozzo.com> <8b98d44a-aeb2-5f5f-2545-ac2bd0c7049b@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8b98d44a-aeb2-5f5f-2545-ac2bd0c7049b@virtuozzo.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.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