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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2DDBC54EE9 for ; Thu, 22 Sep 2022 19:18:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232267AbiIVTSK (ORCPT ); Thu, 22 Sep 2022 15:18:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33270 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230216AbiIVTSH (ORCPT ); Thu, 22 Sep 2022 15:18:07 -0400 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D2743106A10 for ; Thu, 22 Sep 2022 12:18:06 -0700 (PDT) Received: by mail-pl1-x630.google.com with SMTP id w20so9684016ply.12 for ; Thu, 22 Sep 2022 12:18:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:from:to:cc:subject:date; bh=6I54Hmibv9NNEON21MI/khC1j473zoH5sNcGiz/IqMA=; b=jUjTeh5wzF9Ni5HL8rTLkQmxNzQ3yiyS8+wNt2SvUGZ7nGR9TOlyMyCEWezk93KVou ou2QevkOksC6VOZRj8jeW+2+DYXWx2J6QAZhW+ATh67Uxw4MyS9azJq4UHyOMKdiQtRL KOAB4SghBAL72PCXfYFb8JlkczkehRvHXlchTMaaeJ+yZ6C/nefzrjZXIzptjNLOJQUN LwbiXyZgpUtQmTa6axgSgPmAp9DYre7MlUt66vZXtKwxzpLoXuY8BeG6QuthtCJzEUzX 52/bqPUPaJgJ4wazvClsHtrdj6IHUINvjXnc3KpprM7N+v1MNUlksFtyf7vOwH+qASqZ PEJA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:x-gm-message-state:from:to:cc:subject:date; bh=6I54Hmibv9NNEON21MI/khC1j473zoH5sNcGiz/IqMA=; b=6Fu77+DeKbnRKSIztFg0lisy7AdS+2as2geKIqiZDLlKALClp58xJj+Wf+XPIoyWZK eGWJxaklXVP+NqP8ZExD6ye4wo7BIEhNip+gXKnwcZX5j/Y+9HYI77EYT9Y7lgd6ViyA 5XVmzuVoP7xBi+VrNbXxPPG4ayviItr6/5q5HVWE4HF4NrMthf2TsT3qWmONwyQzV29Q 3VtdlMECy1mQAMknifEtllbZF/IxMpuzNaO/qSMgrO2LSPHgegIjrYo/KDs6tkUkRWj3 nm/Tg168jsXCStA+TWi4Ty70BBpfLGzcSh4X2zdUPYZlmC1XBtGzbG+jrEiq7kWkeU8C k1LA== X-Gm-Message-State: ACrzQf0PqaYm8AM8gIuuF/HAForxv2tSdXQ0MowJo5ENdRrxsNsacTpZ Ae71XioiD1ZTIaMiBpjHfdGMmQ== X-Google-Smtp-Source: AMsMyM489NoZHSzA5ZWkq2GQjXZlU0u91w/tPVdZgrkMTT1zpV5yRKNyvag9xLDJ7g9apnER9eiEVg== X-Received: by 2002:a17:90a:ab91:b0:202:a520:56c9 with SMTP id n17-20020a17090aab9100b00202a52056c9mr17319196pjq.1.1663874285912; Thu, 22 Sep 2022 12:18:05 -0700 (PDT) Received: from [2620:15c:29:203:63de:fb65:f8a7:416b] ([2620:15c:29:203:63de:fb65:f8a7:416b]) by smtp.gmail.com with ESMTPSA id a8-20020a170902900800b00178acc7ef16sm4459509plp.253.2022.09.22.12.18.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Sep 2022 12:18:04 -0700 (PDT) Date: Thu, 22 Sep 2022 12:18:04 -0700 (PDT) From: David Rientjes To: Gang Li cc: Zefan Li , Tejun Heo , Johannes Weiner , Andrew Morton , Michal Hocko , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v1] mm: oom: introduce cpuset oom In-Reply-To: <20220921064710.89663-1-ligang.bdlg@bytedance.com> Message-ID: <18621b07-256b-7da1-885a-c96dfc8244b6@google.com> References: <20220921064710.89663-1-ligang.bdlg@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Sep 2022, Gang Li wrote: > cpuset confine processes to processor and memory node subsets. > When a process in cpuset triggers oom, it may kill a completely > irrelevant process on another numa node, which will not release any > memory for this cpuset. > > It seems that `CONSTRAINT_CPUSET` is not really doing much these > days. Using CONSTRAINT_CPUSET, we can easily achieve node aware oom > killing by selecting victim from the cpuset which triggers oom. > > Suggested-by: Michal Hocko > Signed-off-by: Gang Li Hmm, is this the right approach? If a cpuset results in a oom condition, is there a reason why we'd need to find a process from within that cpuset to kill? I think the idea is to free memory on the oom set of nodes (cpuset.mems) and that can happen by killing a process that is not a member of this cpuset. I understand the challenges of creating a NUMA aware oom killer to target memory that is actually resident on an oom node, but this approach doesn't seem right and could actually lead to pathological cases where a small process trying to fork in an otherwise empty cpuset is repeatedly oom killing when we'd actually prefer to kill a single large process. > --- > This idea comes from a previous patch: > mm, oom: Introduce per numa node oom for CONSTRAINT_MEMORY_POLICY > https://lore.kernel.org/all/YoJ%2FioXwGTdCywUE@dhcp22.suse.cz/ > > Any comments are welcome. > --- > include/linux/cpuset.h | 6 ++++++ > kernel/cgroup/cpuset.c | 17 +++++++++++++++++ > mm/oom_kill.c | 4 ++++ > 3 files changed, 27 insertions(+) > > diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h > index d58e0476ee8e..7475f613ab90 100644 > --- a/include/linux/cpuset.h > +++ b/include/linux/cpuset.h > @@ -178,6 +178,8 @@ static inline void set_mems_allowed(nodemask_t nodemask) > task_unlock(current); > } > > +int cpuset_cgroup_scan_tasks(int (*fn)(struct task_struct *, void *), void *arg); > + > #else /* !CONFIG_CPUSETS */ > > static inline bool cpusets_enabled(void) { return false; } > @@ -299,6 +301,10 @@ static inline bool read_mems_allowed_retry(unsigned int seq) > return false; > } > > +static inline int cpuset_cgroup_scan_tasks(int (*fn)(struct task_struct *, void *), void *arg) > +{ > + return 0; > +} > #endif /* !CONFIG_CPUSETS */ > > #endif /* _LINUX_CPUSET_H */ > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index b474289c15b8..1f1238b4276d 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -3943,6 +3943,23 @@ void cpuset_print_current_mems_allowed(void) > rcu_read_unlock(); > } > > +int cpuset_cgroup_scan_tasks(int (*fn)(struct task_struct *, void *), void *arg) > +{ > + int ret = 0; > + struct cgroup *cgrp; > + struct css_task_iter it; > + struct task_struct *task; > + > + rcu_read_lock(); > + css_task_iter_start(&(task_cs(current)->css), CSS_TASK_ITER_PROCS, &it); > + while (!ret && (task = css_task_iter_next(&it))) > + ret = fn(task, arg); > + css_task_iter_end(&it); > + rcu_read_unlock(); > + > + return ret; > +} > + > /* > * Collection of memory_pressure is suppressed unless > * this flag is enabled by writing "1" to the special > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 46e7e073f137..8cea787b359c 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -367,6 +367,8 @@ static void select_bad_process(struct oom_control *oc) > > if (is_memcg_oom(oc)) > mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc); > + else if (oc->constraint == CONSTRAINT_CPUSET) > + cpuset_cgroup_scan_tasks(oom_evaluate_task, oc); > else { > struct task_struct *p; > > @@ -427,6 +429,8 @@ static void dump_tasks(struct oom_control *oc) > > if (is_memcg_oom(oc)) > mem_cgroup_scan_tasks(oc->memcg, dump_task, oc); > + else if (oc->constraint == CONSTRAINT_CPUSET) > + cpuset_cgroup_scan_tasks(dump_task, oc); > else { > struct task_struct *p; > > -- > 2.20.1 > > >