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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 5F235C433DF for ; Thu, 20 Aug 2020 13:46:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 437812076E for ; Thu, 20 Aug 2020 13:46:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730719AbgHTNqg (ORCPT ); Thu, 20 Aug 2020 09:46:36 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:47108 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729819AbgHTNoO (ORCPT ); Thu, 20 Aug 2020 09:44:14 -0400 Received: from ip5f5af70b.dynamic.kabel-deutschland.de ([95.90.247.11] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1k8kr8-0007Yq-07; Thu, 20 Aug 2020 13:43:50 +0000 Date: Thu, 20 Aug 2020 15:43:48 +0200 From: Christian Brauner To: Michal Hocko Cc: Oleg Nesterov , Suren Baghdasaryan , mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, esyr@redhat.com, christian@kellner.me, areber@redhat.com, shakeelb@google.com, cyphar@cyphar.com, adobriyan@gmail.com, akpm@linux-foundation.org, ebiederm@xmission.com, gladkov.alexey@gmail.com, walken@google.com, daniel.m.jordan@oracle.com, avagin@gmail.com, bernd.edlinger@hotmail.de, john.johansen@canonical.com, laoar.shao@gmail.com, timmurray@google.com, minchan@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary Message-ID: <20200820134348.tmoydr2aawghyfkt@wittgenstein> References: <20200820002053.1424000-1-surenb@google.com> <20200820105555.GA4546@redhat.com> <20200820111349.GE5033@dhcp22.suse.cz> <20200820113023.rjxque4jveo4nj5o@wittgenstein> <20200820114245.GH5033@dhcp22.suse.cz> <20200820124109.GI5033@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200820124109.GI5033@dhcp22.suse.cz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 20, 2020 at 02:41:09PM +0200, Michal Hocko wrote: > On Thu 20-08-20 13:42:56, Michal Hocko wrote: > > On Thu 20-08-20 13:30:23, Christian Brauner wrote: > [...] > > > trying to rely on set_bit() and test_bit() in copy_mm() being atomic and > > > then calling it where Oleg said after the point of no return. > > > > No objections. > > Would something like the following work for you? > > diff --git a/kernel/fork.c b/kernel/fork.c > index 9177a76bf840..25b83f0912a6 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1403,15 +1403,6 @@ static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) > if (clone_flags & CLONE_VM) { > mmget(oldmm); > mm = oldmm; > - if (!(clone_flags & CLONE_SIGHAND)) { > - /* We need to synchronize with __set_oom_adj */ > - mutex_lock(&oom_adj_lock); > - set_bit(MMF_PROC_SHARED, &mm->flags); > - /* Update the values in case they were changed after copy_signal */ > - tsk->signal->oom_score_adj = current->signal->oom_score_adj; > - tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min; > - mutex_unlock(&oom_adj_lock); > - } > goto good_mm; > } > > @@ -1818,6 +1809,19 @@ static __always_inline void delayed_free_task(struct task_struct *tsk) > free_task(tsk); > } > > +static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk) > +{ > + if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) == CLONE_VM) { > + /* We need to synchronize with __set_oom_adj */ > + mutex_lock(&oom_adj_lock); > + set_bit(MMF_PROC_SHARED, &mm->flags); > + /* Update the values in case they were changed after copy_signal */ > + tsk->signal->oom_score_adj = current->signal->oom_score_adj; > + tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min; > + mutex_unlock(&oom_adj_lock); > + } > +} > + > /* > * This creates a new process as a copy of the old one, > * but does not actually start it yet. > @@ -2290,6 +2294,8 @@ static __latent_entropy struct task_struct *copy_process( > trace_task_newtask(p, clone_flags); > uprobe_copy_process(p, clone_flags); > > + copy_oom_score_adj(clone_flags, p); > + > return p; > > bad_fork_cancel_cgroup: This should work, yes. And keeps the patch reasonably small. Christian