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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6925C433F5 for ; Mon, 18 Oct 2021 10:06:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3F42C60F9D for ; Mon, 18 Oct 2021 10:06:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 3F42C60F9D Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id A7127900002; Mon, 18 Oct 2021 06:06:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A211A6B0071; Mon, 18 Oct 2021 06:06:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 90FB0900002; Mon, 18 Oct 2021 06:06:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0041.hostedemail.com [216.40.44.41]) by kanga.kvack.org (Postfix) with ESMTP id 7FF196B006C for ; Mon, 18 Oct 2021 06:06:05 -0400 (EDT) Received: from smtpin34.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 3FBC51837CD74 for ; Mon, 18 Oct 2021 10:06:05 +0000 (UTC) X-FDA: 78709127490.34.110ABEA Received: from relay.sw.ru (relay.sw.ru [185.231.240.75]) by imf03.hostedemail.com (Postfix) with ESMTP id E6EAF30000AA for ; Mon, 18 Oct 2021 10:06:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=v4LeNmv3SwkPyguGAt7spZmFtAAdvhXagti3/HiYcJM=; b=r4Z5e0aOk/6+/4aZs d7663+ojeE6T0F6uJmOyL5Pz4218rmSSlZlOHAF0M1+A5jfWkm9VZQCR2reaIs6T5hlleLq2aGsdg /Lhhr8JbHMWL41nqvxptFCnM/ocSlQ/Z1BSsugLOrY81bJhOtJymU6dG8cwLy0kVZ+3C9JuHXUfjs =; Received: from [172.29.1.17] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mcPWm-006Kzj-DN; Mon, 18 Oct 2021 13:05:56 +0300 Subject: Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Roman Gushchin , Uladzislau Rezki , Vlastimil Babka , Shakeel Butt , Mel Gorman , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@openvz.org References: <9d10df01-0127-fb40-81c3-cc53c9733c3e@virtuozzo.com> From: Vasily Averin Message-ID: <6b751abe-aa52-d1d8-2631-ec471975cc3a@virtuozzo.com> Date: Mon, 18 Oct 2021 13:05:35 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Stat-Signature: dd535byqbsd8cy3e6hef99uo9ofokkn9 Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=virtuozzo.com header.s=relay header.b=r4Z5e0aO; spf=pass (imf03.hostedemail.com: domain of vvs@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=vvs@virtuozzo.com; dmarc=pass (policy=quarantine) header.from=virtuozzo.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E6EAF30000AA X-HE-Tag: 1634551562-34591 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 18.10.2021 12:04, Michal Hocko wrote: > On Mon 18-10-21 11:13:52, Vasily Averin wrote: > [...] >> How could this happen? >> >> User-space task inside the memcg-limited container generated a page fault, >> its handler do_user_addr_fault() called handle_mm_fault which could not >> allocate the page due to exceeding the memcg limit and returned VM_FAULT_OOM. >> Then do_user_addr_fault() called pagefault_out_of_memory() which executed >> out_of_memory() without set of memcg. >> >> Partially this problem depends on one of my recent patches, disabled unlimited >> memory allocation for dying tasks. However I think the problem can happen >> on non-killed tasks too, for example because of kmem limit. > > Could you be more specific on how this can happen without your patch? I > have to say I haven't realized this side effect when discussing it. We can reach obj_cgroup_charge_pages() for example via do_user_addr_fault handle_mm_fault __handle_mm_fault p4d_alloc __p4d_alloc p4d_alloc_one get_zeroed_page __get_free_pages alloc_pages __alloc_pages __memcg_kmem_charge_page obj_cgroup_charge_pages Here we call try_charge_memcg() that return success and approve the allocation, however then we hit into kmem limit and fail the allocation. If required I can try to search how try_charge_memcg() can reject page allocation of non-dying task too. > I will be honest that I am not really happy about pagefault_out_of_memory. > I have tried to remove it in the past. Without much success back then, > unfortunately[1]. > Maybe we should get rid of it finally. The OOM is always triggered from > inside the allocator where we have much more infromation about the > allocation context. A first step would be to skip pagefault_out_of_memory > for killed or exiting processes. I like this idea, however it may be not enough, at least in scenario described above. > [1] I do not have msg-id so I cannot provide a lore link but google > pointed me to https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1400402.html Thank you, I'll read this discussion. Vasily Averin