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=-0.6 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,T_DKIM_INVALID autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 31C26C5CFF1 for ; Tue, 12 Jun 2018 14:07:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DAA8E2089C for ; Tue, 12 Jun 2018 14:07:14 +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="phReSwzU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DAA8E2089C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933938AbeFLOHN (ORCPT ); Tue, 12 Jun 2018 10:07:13 -0400 Received: from merlin.infradead.org ([205.233.59.134]:51220 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932749AbeFLOHM (ORCPT ); Tue, 12 Jun 2018 10:07:12 -0400 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: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=k9lVHYRt0Iiu0WcB+6hdvoLzY4VGCFinlG/XINzhYjU=; b=phReSwzUphSGLqec65OtN2RHS Idh+M/PHwT9dhKFDlkp23Ij7tyQ1JA1FK6Com8CeMp0FQ57eXNj61ssZtsg/jLaN4NHwoHIdYDgAE GhIglLcVmEWaWyPAQtqmpbtTkFx7rkO3uB+Ds6pGK3zeWKfzUd8hdC+EKQApiFz1+yvXJO6/s2DGB YXtgP1H7BNaiJN9JGptUNFSbkdMinOWZ8jpByxn92mJsm7+2UsQ8vlCnilCZnEG3GS8uGfeufwVr2 ZwMyMawSwxA+2Q+NpHFCXQvJKINBOxXUzeJWnDijBCrQtQ+OymP1cIRzr38bnTIxJv4dlFJJXQVSw EWTTTxWLg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fSjwm-0003to-8R; Tue, 12 Jun 2018 14:06:56 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 512FB201EA7CD; Tue, 12 Jun 2018 16:06:54 +0200 (CEST) Date: Tue, 12 Jun 2018 16:06:54 +0200 From: Peter Zijlstra To: Daniel Lezcano Cc: viresh.kumar@linaro.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Eduardo Valentin , Javi Merino , Leo Yan , Kevin Wangtao , Vincent Guittot , Rui Zhang , Daniel Thompson , Andrea Parri Subject: Re: [PATCH V6] powercap/drivers/idle_injection: Add an idle injection framework Message-ID: <20180612140654.GQ12217@hirez.programming.kicks-ass.net> References: <1528804816-32636-1-git-send-email-daniel.lezcano@linaro.org> <20180612123036.GJ12180@hirez.programming.kicks-ass.net> <16d5649d-863c-10c7-9287-202568e713e6@linaro.org> <20180612125247.GO12217@hirez.programming.kicks-ass.net> <16770447-afe3-0fd7-19f9-1bd52c4c8ced@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16770447-afe3-0fd7-19f9-1bd52c4c8ced@linaro.org> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 12, 2018 at 03:02:14PM +0200, Daniel Lezcano wrote: > On 12/06/2018 14:52, Peter Zijlstra wrote: > > In this case, you can do: > > That is what we had before but we change the code to set the count > before waking up the task, so compute the cpumask_weight of the > resulting AND right before this loop. > > > + for_each_cpu_and(cpu, &ii_dev->cpumask, cpu_online_mask) { > > + iit = per_cpu_ptr(&idle_injection_thread, cpu); > > + iit->should_run = 1; > > + wake_up_process(iit->tsk); > > + } Ah, I see, but since you do: if (atomic_dec_and_test()) last_man() where that last_man() thing will start a timer, there is no real problem with doing atomic_inc() with before wake_up_process(). Yes, it allows doing last_man, too often, but repeated hrtimer_start() will DTRT and reprogram the timer. Also, last_man() uses @run_duration, but the way I read it, the timer is for waking things up again, this means it is in fact the sleep duration, no? Furthermore, should you not be using hrtimer_forward(&timer, idle_duration + run_duration) instead? AFAICT the current scheme is prone to drifting.