From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758057Ab2HJI5w (ORCPT ); Fri, 10 Aug 2012 04:57:52 -0400 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:45829 "EHLO LGEMRELSE7Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757948Ab2HJI5s (ORCPT ); Fri, 10 Aug 2012 04:57:48 -0400 X-AuditID: 9c930197-b7bb2ae0000011d9-e6-5024cd0a4ffc From: Namhyung Kim To: Mike Galbraith Cc: Ingo Molnar , Peter Zijlstra , LKML , Namhyung Kim , Suresh Siddha Subject: Re: [RFC/PATCH] sched: Honor sync wake up in select_idle_sibling References: <1344583512-25352-1-git-send-email-namhyung@kernel.org> <1344586484.4330.24.camel@marge.simpson.net> Date: Fri, 10 Aug 2012 17:51:58 +0900 In-Reply-To: <1344586484.4330.24.camel@marge.simpson.net> (Mike Galbraith's message of "Fri, 10 Aug 2012 10:14:44 +0200") Message-ID: <87boijw2mp.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Mike On Fri, 10 Aug 2012 10:14:44 +0200, Mike Galbraith wrote: > On Fri, 2012-08-10 at 16:25 +0900, Namhyung Kim wrote: >> From: Namhyung Kim >> >> When sync wakeup happens and there's the waker task running alone, >> select the target cpu as if it's already idle. > > Ouch. That defeats the purpose of select_idle_sibling(). Just because > we're doing a sync wakeup does not mean there's no convertible overlap, > nor that the waker is really really going to take a nap immediately. A > lot of the places that benefit up to and including hugely from looking > for an idle shared cache to wake to do sync wakeups. Thanks for the explanation! I misunderstood the function ;) Thanks, Namhyung