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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00B8DC433EF for ; Mon, 4 Jul 2022 15:12:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6BC356B0072; Mon, 4 Jul 2022 11:12:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 66C606B0073; Mon, 4 Jul 2022 11:12:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 535B36B0074; Mon, 4 Jul 2022 11:12:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 4614A6B0072 for ; Mon, 4 Jul 2022 11:12:57 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 1A6B98067D for ; Mon, 4 Jul 2022 15:12:57 +0000 (UTC) X-FDA: 79649759994.01.2BDCED2 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf28.hostedemail.com (Postfix) with ESMTP id 80C1EC0051 for ; Mon, 4 Jul 2022 15:12:56 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 500211FD39; Mon, 4 Jul 2022 15:12:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1656947575; 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=oVYS4bUOdNSsnRwjamBfXVxY7OYzKvz0dEnKnULT0m0=; b=vOdePtXjqkrtYTUiDZM/PSpsWTz3hI/lFsIqeA7Te+9fPmJnmkUo6UsDy3Lw8zQifjAOmj jGKhW6fCofSwiJadpjagD0gBDjoctYt6jNKPjCTcaeJaquJzE7jNXSpG/X6hpycqMcSAyZ RyYqM5I9fvWSREHqqKaoaAinKDszAvE= 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 1A7562C141; Mon, 4 Jul 2022 15:12:55 +0000 (UTC) Date: Mon, 4 Jul 2022 17:12:54 +0200 From: Michal Hocko To: Roman Gushchin Cc: Andrew Morton , Yafang Shao , Johannes Weiner , Shakeel Butt , Muchun Song , cgroups@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Subject: Re: [PATCH] mm: memcontrol: do not miss MEMCG_MAX events for enforced allocations Message-ID: References: <20220702033521.64630-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220702033521.64630-1-roman.gushchin@linux.dev> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656947576; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=oVYS4bUOdNSsnRwjamBfXVxY7OYzKvz0dEnKnULT0m0=; b=ojxwjSHaeVpEN3jp1MQAC6UvnkN2HXtCMxkEWJGFreoskNezVxRkiZyGwFpqo6xb4GSqGd xEryLTSjgCKBcXYOszCVErKlQGtFw8GD/9Ais/h51TZ/+Gat3kB0LdWZgMtSCaRgsiVgJG 7DyVr7Hs4pL++6+VYmKyicHtWWTRyh4= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=vOdePtXj; spf=pass (imf28.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656947576; a=rsa-sha256; cv=none; b=46bNSGcwoiLqIhxIgfmhSxVQQL0Zw+y2cY2hC+SnZuTkv0kwdiiRrE36riAI9+3j589DC5 Nws23U1OfTXdEfmu7jYhGifPCF/agXB6eXRhxGFkuqU9AwLuX3Yj9WAHNnxO6OulcjBUUb Poj7GaMvKlZ7siwRZCdOhkMyAP8+Eq0= X-Stat-Signature: jntxjz9ioqu3nzcmo388trfedoeokdy6 X-Rspamd-Queue-Id: 80C1EC0051 Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=vOdePtXj; spf=pass (imf28.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1656947576-990475 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri 01-07-22 20:35:21, Roman Gushchin wrote: > Yafang Shao reported an issue related to the accounting of bpf > memory: if a bpf map is charged indirectly for memory consumed > from an interrupt context and allocations are enforced, MEMCG_MAX > events are not raised. So I guess this will be a GFP_ATOMIC request failing due to the hard limit, right? I think it would be easier to understand if the specific allocation request type was mentioned. > It's not/less of an issue in a generic case because consequent > allocations from a process context will trigger the reclaim and > MEMCG_MAX events. However a bpf map can belong to a dying/abandoned > memory cgroup, so it might never happen. So the cgroup can > significantly exceed the memory.max limit without even triggering > MEMCG_MAX events. More on that in other reply. > Fix this by making sure that we never enforce allocations without > raising a MEMCG_MAX event. > > Reported-by: Yafang Shao > Signed-off-by: Roman Gushchin > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Shakeel Butt > Cc: Muchun Song > Cc: cgroups@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: bpf@vger.kernel.org The patch makes sense to me though even without the weird charge to a dead memcg aspect. It is true that a very calm memcg can trigger the even much later after a GFP_ATOMIC charge (or __GFP_HIGH in general) fails. Acked-by: Michal Hocko > --- > mm/memcontrol.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 655c09393ad5..eb383695659a 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2577,6 +2577,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > bool passed_oom = false; > bool may_swap = true; > bool drained = false; > + bool raised_max_event = false; > unsigned long pflags; > > retry: > @@ -2616,6 +2617,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > goto nomem; > > memcg_memory_event(mem_over_limit, MEMCG_MAX); > + raised_max_event = true; > > psi_memstall_enter(&pflags); > nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages, > @@ -2682,6 +2684,13 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > if (!(gfp_mask & (__GFP_NOFAIL | __GFP_HIGH))) > return -ENOMEM; > force: > + /* > + * If the allocation has to be enforced, don't forget to raise > + * a MEMCG_MAX event. > + */ > + if (!raised_max_event) > + memcg_memory_event(mem_over_limit, MEMCG_MAX); > + > /* > * The allocation either can't fail or will lead to more memory > * being freed very soon. Allow memory usage go over the limit > -- > 2.36.1 -- Michal Hocko SUSE Labs