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=-19.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 DC94EC433EF for ; Mon, 13 Sep 2021 10:35:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C265C60F9B for ; Mon, 13 Sep 2021 10:35:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239104AbhIMKgW (ORCPT ); Mon, 13 Sep 2021 06:36:22 -0400 Received: from relay.sw.ru ([185.231.240.75]:42532 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235123AbhIMKgT (ORCPT ); Mon, 13 Sep 2021 06:36:19 -0400 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=JtnXdiyIXGAC109gjCty025cKhFakGINc+ixRMlNDpA=; b=A+qYkWFCnoHTc649z HHLFN2PQHVW+RQhZp5w5+2cbHQTq1eQVtFctCPop4AQ2O6l1lZR3yYepfmSnBPbrqITSivRv2+pqX tbp2/oezk8tLXe94ZguInAw4zdietPjN+h/L0pJm7V4tb4VC1shs+tdbXGXbVf3TZkucEPZVrYfDI =; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mPjIk-001oDU-0G; Mon, 13 Sep 2021 13:35:02 +0300 Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Tetsuo Handa , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <5b06a490-55bc-a6a0-6c85-690254f86fad@virtuozzo.com> From: Vasily Averin Message-ID: <7af26106-388c-6f99-e018-669a8f0cf9b5@virtuozzo.com> Date: Mon, 13 Sep 2021 13:35:00 +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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/13/21 11:53 AM, Michal Hocko wrote: > On Fri 10-09-21 15:39:28, 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. >> Moreover lifetime of the allocated object can differ from >> In addition the lifetime of the dying task. >> Multiple such allocations running concurrently can not only overuse >> the memcg limit, but can lead to a global out of memory and, >> in the worst case, cause the host to panic. >> >> Signed-off-by: Vasily Averin >> --- >> mm/memcontrol.c | 23 +++++------------------ >> 1 file changed, 5 insertions(+), 18 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 389b5766e74f..67195fcfbddf 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -1834,6 +1834,9 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int >> return OOM_ASYNC; >> } >> >> + if (should_force_charge()) >> + return OOM_SKIPPED; > > mem_cgroup_out_of_memory already check for the bypass, now you are > duplicating that check with a different answer to the caller. This is > really messy. One of the two has to go away. In this case mem_cgroup_out_of_memory() takes locks and mutexes but doing nothing useful and its success causes try_charge_memcg() to repeat the loop unnecessarily. I cannot change mem_cgroup_out_of_memory internals, because it is used in other places too.The check inside mem_cgroup_out_of_memory is required because situation can be changed after check added into mem_cgroup_oom(). Though I got your argument, and will think how to improve the patch. Anyway we'll need to do something with name of should_force_charge() function that will NOT lead to forced charge. Thank you, Vasily Averin Thank you, From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vasily Averin Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks Date: Mon, 13 Sep 2021 13:35:00 +0300 Message-ID: <7af26106-388c-6f99-e018-669a8f0cf9b5@virtuozzo.com> References: <5b06a490-55bc-a6a0-6c85-690254f86fad@virtuozzo.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: 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=JtnXdiyIXGAC109gjCty025cKhFakGINc+ixRMlNDpA=; b=A+qYkWFCnoHTc649z HHLFN2PQHVW+RQhZp5w5+2cbHQTq1eQVtFctCPop4AQ2O6l1lZR3yYepfmSnBPbrqITSivRv2+pqX tbp2/oezk8tLXe94ZguInAw4zdietPjN+h/L0pJm7V4tb4VC1shs+tdbXGXbVf3TZkucEPZVrYfDI =; In-Reply-To: Content-Language: en-US List-ID: Content-Type: text/plain; charset="us-ascii" To: Michal Hocko 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 9/13/21 11:53 AM, Michal Hocko wrote: > On Fri 10-09-21 15:39:28, 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. >> Moreover lifetime of the allocated object can differ from >> In addition the lifetime of the dying task. >> Multiple such allocations running concurrently can not only overuse >> the memcg limit, but can lead to a global out of memory and, >> in the worst case, cause the host to panic. >> >> Signed-off-by: Vasily Averin >> --- >> mm/memcontrol.c | 23 +++++------------------ >> 1 file changed, 5 insertions(+), 18 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 389b5766e74f..67195fcfbddf 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -1834,6 +1834,9 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int >> return OOM_ASYNC; >> } >> >> + if (should_force_charge()) >> + return OOM_SKIPPED; > > mem_cgroup_out_of_memory already check for the bypass, now you are > duplicating that check with a different answer to the caller. This is > really messy. One of the two has to go away. In this case mem_cgroup_out_of_memory() takes locks and mutexes but doing nothing useful and its success causes try_charge_memcg() to repeat the loop unnecessarily. I cannot change mem_cgroup_out_of_memory internals, because it is used in other places too.The check inside mem_cgroup_out_of_memory is required because situation can be changed after check added into mem_cgroup_oom(). Though I got your argument, and will think how to improve the patch. Anyway we'll need to do something with name of should_force_charge() function that will NOT lead to forced charge. Thank you, Vasily Averin Thank you,