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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 7C26DC2F421 for ; Mon, 21 Jan 2019 14:59:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4AB0F20870 for ; Mon, 21 Jan 2019 14:59:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="lfMXZm5h" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729890AbfAUO7k (ORCPT ); Mon, 21 Jan 2019 09:59:40 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:48940 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729474AbfAUO7j (ORCPT ); Mon, 21 Jan 2019 09:59:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=+XkP6BjBOoguOx02ypGLg2Qbad4YbXufumxqfvbyOgo=; b=lfMXZm5hjEwlCw+4TqCeYF5mM kvenuIAuRzFYsU/vhChWqDhCjjEpHQZ7xOPkUtsYKMtnughlRpUAogubV+1uSmTEbZg0Hi5jR4lmg u2wO7Sx15bYX2/qw3Izqapybq0LC4o9QPoVidVURmrBP8qb9OPcO3ynW9h5wZDiBxj/vhko0AlskK vHq1CE9Pzb8PSI4ZAF1Lo8O1MeTKE6zz0VgT/F98qZup3ZfeuDTqbbGAIH4sJLM0GQUJ+tL83eZuv R1S3UD9J8AQZ+U2U3q/CONzYTaTfp8M93v4lGzJrO23Fht72zoMKUNMqWZhbu6YwV8asnBm9Oi9Zq 5WiFWnLIQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1glb2y-00063P-6z; Mon, 21 Jan 2019 14:59:32 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 91FF8284706C0; Mon, 21 Jan 2019 15:59:29 +0100 (CET) Date: Mon, 21 Jan 2019 15:59:29 +0100 From: Peter Zijlstra To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org, Ingo Molnar , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v6 04/16] sched/core: uclamp: Add CPU's clamp buckets refcounting Message-ID: <20190121145929.GI27931@hirez.programming.kicks-ass.net> References: <20190115101513.2822-1-patrick.bellasi@arm.com> <20190115101513.2822-5-patrick.bellasi@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190115101513.2822-5-patrick.bellasi@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 15, 2019 at 10:15:01AM +0000, Patrick Bellasi wrote: > @@ -835,6 +954,28 @@ static void uclamp_bucket_inc(struct uclamp_se *uc_se, unsigned int clamp_id, > } while (!atomic_long_try_cmpxchg(&uc_maps[bucket_id].adata, > &uc_map_old.data, uc_map_new.data)); > > + /* > + * Ensure each CPU tracks the correct value for this clamp bucket. > + * This initialization of per-CPU variables is required only when a > + * clamp value is requested for the first time from a slow-path. > + */ I'm confused; why is this needed? > + if (unlikely(!uc_map_old.se_count)) { > + for_each_possible_cpu(cpu) { > + struct uclamp_cpu *uc_cpu = > + &cpu_rq(cpu)->uclamp[clamp_id]; > + > + /* CPU's tasks count must be 0 for free buckets */ > + SCHED_WARN_ON(uc_cpu->bucket[bucket_id].tasks); > + if (unlikely(uc_cpu->bucket[bucket_id].tasks)) > + uc_cpu->bucket[bucket_id].tasks = 0; > + > + /* Minimize cache lines invalidation */ > + if (uc_cpu->bucket[bucket_id].value == bucket_value) > + continue; > + uc_cpu->bucket[bucket_id].value = bucket_value; > + } > + } > + > uc_se->value = clamp_value; > uc_se->bucket_id = bucket_id; >