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=-6.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 1105EC41604 for ; Wed, 7 Oct 2020 16:55:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8216221582 for ; Wed, 7 Oct 2020 16:55:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="hHCdo69g" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727927AbgJGQzv (ORCPT ); Wed, 7 Oct 2020 12:55:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54534 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726956AbgJGQzv (ORCPT ); Wed, 7 Oct 2020 12:55:51 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E1B8CC061755 for ; Wed, 7 Oct 2020 09:55:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=sxbkS3NRMl6rIsLLVu2DdPxndxYXSPWPV6laeejVFsU=; b=hHCdo69g1ERO0IyETSWyJVT5Gn BLeZEqM1CGzKvDiaGp273w5dx+Abx7FxWkr2A1qq6zGnEZCNr2FIBXZUxDbX3UrnXT0RzltPzr/D6 9Z8zo+4bDSJ9oeOaizYam7gbczI0WF0Dd/N4GZSs3mHTj4vSmFYpRuV56M+WZmx4Eb6SJuvwL7kul X9Xfn7mUj0Z8U30JBcyaVd+PLOZSQcCVJb5pf73KafT0byRiYj8dx51haG1ytZA/0DgX1GA7tA72b HPQqgvdK2qNxUaG/x4PWhRiCTA0ZphN2ZwjTpiqZwcxuxfoVWEQ8EWyBcVCXJkFteS4EWk8RVNZQI y3tf9o4g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQCj1-0004Ix-Gi; Wed, 07 Oct 2020 16:55:35 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 997B83019CE; Wed, 7 Oct 2020 18:55:33 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 815322B067BD9; Wed, 7 Oct 2020 18:55:33 +0200 (CEST) Date: Wed, 7 Oct 2020 18:55:33 +0200 From: Peter Zijlstra To: Peng Liu Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, valentin.schneider@arm.com, raistlin@linux.it Subject: Re: [PATCH v5 1/2] sched/deadline: optimize sched_dl_global_validate() Message-ID: <20201007165533.GL2628@hirez.programming.kicks-ass.net> References: <9ad8eff54a3dd6f7f0da50e827047e4d3c4bb00a.1601993091.git.iwtbavbm@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9ad8eff54a3dd6f7f0da50e827047e4d3c4bb00a.1601993091.git.iwtbavbm@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 07, 2020 at 11:12:29PM +0800, Peng Liu wrote: > +/* Used for dl_bw check and update. */ > +static u32 dl_generation; > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 28709f6b0975..53477e8b26b0 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -798,6 +798,13 @@ struct root_domain { > */ > cpumask_var_t dlo_mask; > atomic_t dlo_count; > + > + /* > + * Indicate whether a root_domain's dl_bw has been checked or > + * updated. It's monotonously increasing, then wrap around. > + */ > + u32 visit_gen; > + > struct dl_bw dl_bw; > struct cpudl cpudl; > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index dd7770226086..90f3e5558fa2 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -516,6 +516,7 @@ static int init_rootdomain(struct root_domain *rd) > init_irq_work(&rd->rto_push_work, rto_push_irq_work_func); > #endif > > + rd->visit_gen = 0; > init_dl_bw(&rd->dl_bw); > if (cpudl_init(&rd->cpudl) != 0) > goto free_rto_mask; I'm fairly sure I made the generation a u64, the above is susceptible to a false positive due to wrap-around. Increase the generation to -1, create a new root domain, then the next generation is 0 and we'll skip the new domain, even though it should be updated.