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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0321CC433EF for ; Thu, 28 Oct 2021 16:19:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D408C6103C for ; Thu, 28 Oct 2021 16:19:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230156AbhJ1QVm (ORCPT ); Thu, 28 Oct 2021 12:21:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57154 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229565AbhJ1QVk (ORCPT ); Thu, 28 Oct 2021 12:21:40 -0400 Received: from out10.migadu.com (out10.migadu.com [IPv6:2001:41d0:2:e8e3::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94400C061570 for ; Thu, 28 Oct 2021 09:19:13 -0700 (PDT) Date: Fri, 29 Oct 2021 00:19:48 +0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1635437951; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=UKnFFiMfY0GxswzJmBjzLfl2Fj5DavTAFzb8a7nWObQ=; b=IMBJdvx4lTA/0WJec4tnZEwkaCDtgWkK6vn7ZWf+VhH4bFLgkkGfrYY2Eb/yg2GWRxuNdI WQX41RpqvbTCU/OcCdkcZy+JU7Z5BztpoBWQhr7cAhMGejXHNxq7R3QaPi2J9wEFo323yU jI1+q8H5txYSq6+eCyKpY4xGNpOYBlk= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Tao Zhou To: Mel Gorman Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , Valentin Schneider , Aubrey Li , Barry Song , Mike Galbraith , Srikar Dronamraju , LKML , Tao Zhou Subject: Re: [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers Message-ID: References: <20211028094834.1312-1-mgorman@techsingularity.net> <20211028094834.1312-2-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211028094834.1312-2-mgorman@techsingularity.net> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: tao.zhou@linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mel, On Thu, Oct 28, 2021 at 10:48:33AM +0100, Mel Gorman wrote: > @@ -5865,6 +5865,14 @@ static void record_wakee(struct task_struct *p) > } > > if (current->last_wakee != p) { > + int min = __this_cpu_read(sd_llc_size) << 1; > + /* > + * Couple the wakee flips to the waker for the case where it > + * doesn't accrue flips, taking care to not push the wakee > + * high enough that the wake_wide() heuristic fails. > + */ > + if (current->wakee_flips > p->wakee_flips * min) > + p->wakee_flips++; > current->last_wakee = p; > current->wakee_flips++; > } > @@ -5895,7 +5903,7 @@ static int wake_wide(struct task_struct *p) > > if (master < slave) > swap(master, slave); > - if (slave < factor || master < slave * factor) > + if ((slave < factor && master < (factor>>1)*factor) || master < slave * factor) So, the check like this include the above range: if ((slave < factor && master < slave * factor) || master < slave * factor) That "factor>>1" filter some. If "slave < factor" is true and "master < (factor>>1)*factor" is false, then we check "master < slave * factor".(This is one path added by the check "&& master < (factor>>1)*factor"). In the latter check "slave < factor" must be true, the result of this check depend on slave in the range [factor, factor>>1] if there is possibility that "master < slave * factor". If slave in [factor>>1, 0], the check of "master < slave * factor" is absolutly false and this can be filtered if we use a variable to load the result of master < (factor>>1)*factor. My random random inputs and continue confusing to move on. Thanks, Tao