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spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=n79iA6hvbyPNyLso4hAHwfWy1T/M0EJ1WAcJkSLveSc=; b=z2Hj95BfJ67S3jlVf1OTeJdiW 6MSDPPjr15fU5V/HZWxJhiSnoq1QptEINGXya0lgUHht2YNZmzDx+348xKwjn3h1PvsreHszux8fO u4LDlkcQq3fFFicXLE5TfU4fIEmhh2A2ilisb8HfsUCY5D5/MvyW0mFEzlx1za6C93zAIbvWp+0Nz h3F/zI4eQ1YXiE5GClGCbGzowINq4PDg7FQZQgHs5ZM+k05WVvMpE44Tm884vJKet2sHcQ0J409iA Ghz8/J2yWlOUm55cZFMPIx4KjdJqn8vywno0QRGHwMRXJX//Ptb5HBY8eaBh7sHQ5jaq59ZtUr1nG ZyFOItrNQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kpulB-0007EG-Cz; Thu, 17 Dec 2020 15:00:05 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kpul8-0007D1-GT for linux-arm-kernel@lists.infradead.org; Thu, 17 Dec 2020 15:00:03 +0000 Date: Thu, 17 Dec 2020 14:59:54 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1608217201; bh=SryEihmoGHKC5r1tLLVQJV4OdHijgIVYH18Si4+ZQUE=; h=From:To:Cc:Subject:References:In-Reply-To:From; b=N22OMxb+xaAjqkpCj4d3MHixRyNQhPXV6rdtIQ15RNVqNQeprGTLVAd20egsnrxJY uOSYgL8oU5NSCqc52q24+/d0n6RFicWy26aoTiR8Ohqb2TMnSA7YqXYaDDA06T3h9R evanQ6FiSR/bOONjtVrKzXXJgMedjO686WaL35XToPghTZB9DrIeuBzUQtJAQqzIqa 43uHKXNHr1PPswqSI592mhRYcyvFB3ppLEhUPpag9ct0eabMRS/H0zmH4RDiCyv+HG ue7W0nBnopnMCer75U/CLVzAxUXfkEQ9tq31m1EgzuxwbwD/J1tZfCQWUm2ZNY4SAq x2wufl1GC+/OA== From: Will Deacon To: Peter Zijlstra Subject: Re: [PATCH v5 07/15] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Message-ID: <20201217145954.GA17881@willie-the-truck> References: <20201208132835.6151-1-will@kernel.org> <20201208132835.6151-8-will@kernel.org> <20201217121552.ds7g2icvqp5nvtha@e107158-lin.cambridge.arm.com> <20201217134401.GY3040@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201217134401.GY3040@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201217_100002_789192_436F2218 X-CRM114-Status: GOOD ( 23.68 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Juri Lelli , kernel-team@android.com, Vincent Guittot , Ingo Molnar , Greg Kroah-Hartman , Catalin Marinas , Quentin Perret , linux-kernel@vger.kernel.org, Morten Rasmussen , Johannes Weiner , Li Zefan , Marc Zyngier , Tejun Heo , Suren Baghdasaryan , Qais Yousef , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Dec 17, 2020 at 02:44:01PM +0100, Peter Zijlstra wrote: > On Thu, Dec 17, 2020 at 12:15:52PM +0000, Qais Yousef wrote: > > On 12/08/20 13:28, Will Deacon wrote: > > > If the scheduler cannot find an allowed CPU for a task, > > > cpuset_cpus_allowed_fallback() will widen the affinity to cpu_possible_mask > > > if cgroup v1 is in use. > > > > > > In preparation for allowing architectures to provide their own fallback > > > mask, just return early if we're not using cgroup v2 and allow > > > select_fallback_rq() to figure out the mask by itself. > > > > > > Cc: Li Zefan > > > Cc: Tejun Heo > > > Cc: Johannes Weiner > > > Reviewed-by: Quentin Perret > > > Signed-off-by: Will Deacon > > > --- > > > kernel/cgroup/cpuset.c | 6 ++++-- > > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > > > index 57b5b5d0a5fd..e970737c3ed2 100644 > > > --- a/kernel/cgroup/cpuset.c > > > +++ b/kernel/cgroup/cpuset.c > > > @@ -3299,9 +3299,11 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) > > > > > > void cpuset_cpus_allowed_fallback(struct task_struct *tsk) > > > { > > > + if (!is_in_v2_mode()) > > > + return; /* select_fallback_rq will try harder */ > > > + > > > rcu_read_lock(); > > > - do_set_cpus_allowed(tsk, is_in_v2_mode() ? > > > - task_cs(tsk)->cpus_allowed : cpu_possible_mask); > > > + do_set_cpus_allowed(tsk, task_cs(tsk)->cpus_allowed); > > > > Why is it safe to return that for cpuset v2? > > v1 > > Because in that case it does cpu_possible_mask, which, if you look at > select_fallback_rq(), is exactly what happens when cpuset 'fails' to > find a candidate. > > Or at least, that's how I read the patch. I think Qais a point with v2 though: if task_cs(tsk)->cpus_allowed contains 64-bit-only CPUs, then we're in trouble here. I should be taking the intersection with the task_cpu_possible_mask() for the task. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel