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 7132DC433EF for ; Mon, 18 Oct 2021 11:53:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5790660F02 for ; Mon, 18 Oct 2021 11:53:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231495AbhJRL4H (ORCPT ); Mon, 18 Oct 2021 07:56:07 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:37654 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230048AbhJRL4F (ORCPT ); Mon, 18 Oct 2021 07:56:05 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id C710221A88; Mon, 18 Oct 2021 11:53:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1634558033; 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=z0UuFhyEIjaBwP5r+PsHqxA5xRPhuNYdcMZlskEMrGY=; b=ZjqWXdfXKMHPd/7dT3ZBbyBYZT0GvgAZ5uFgml9vKheBX4/odRHnrEAofs7gvFBKL4fXSS QqzjjM9mDqd1EmrGjEllilhLo4/Pl972XwkKlQ/ZZD5galvGZzeue6+WzkaFo16XZqbkRh O4YcNdXLvw0yWOgMbWzLZcivjA/nvDg= 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 642DDA3B89; Mon, 18 Oct 2021 11:53:53 +0000 (UTC) Date: Mon, 18 Oct 2021 13:53:43 +0200 From: Michal Hocko To: Vasily Averin 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 Subject: Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task Message-ID: References: <9d10df01-0127-fb40-81c3-cc53c9733c3e@virtuozzo.com> <6b751abe-aa52-d1d8-2631-ec471975cc3a@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6b751abe-aa52-d1d8-2631-ec471975cc3a@virtuozzo.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 18-10-21 13:05:35, Vasily Averin wrote: > 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. Just to make sure I understand this would be for the v1 kmem explicit limit, correct? > If required I can try to search how try_charge_memcg() can reject page allocation > of non-dying task too. Yes. > > 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. I original patch has removed the oom killer completely. -- Michal Hocko SUSE Labs