From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757355Ab3AIHyP (ORCPT ); Wed, 9 Jan 2013 02:54:15 -0500 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:47554 "EHLO LGEMRELSE7Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757273Ab3AIHyO (ORCPT ); Wed, 9 Jan 2013 02:54:14 -0500 X-AuditID: 9c930197-b7cefae0000002d7-44-50ed22247092 From: Namhyung Kim To: Alex Shi Cc: Ingo Molnar , Peter Zijlstra , LKML , Namhyung Kim , Mike Galbraith , Preeti U Murthy , Vincent Guittot Subject: Re: [PATCH] sched: Get rid of unnecessary checks from select_idle_sibling References: <1357714256-24373-1-git-send-email-namhyung@kernel.org> <50ED1D54.70208@intel.com> Date: Wed, 09 Jan 2013 16:54:09 +0900 In-Reply-To: <50ED1D54.70208@intel.com> (Alex Shi's message of "Wed, 09 Jan 2013 15:33:40 +0800") Message-ID: <876236rdum.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 Alex, On Wed, 09 Jan 2013 15:33:40 +0800, Alex Shi wrote: > On 01/09/2013 02:50 PM, Namhyung Kim wrote: >> From: Namhyung Kim >> >> AFAICS @target cpu of select_idle_sibling() is always either prev_cpu >> or this_cpu. So no need to check it again and the conditionals can be >> consolidated. [snip] > Uh, we don't know if the target is this_cpu or previous cpu, If we just > check the target idle status, we may miss another idle cpu. So this > patch change the logical in this function. select_idle_sibling() is called only in select_task_rq_fair() if it found a suitable affine_sd. The default target is the 'prev_cpu' of the task but if wake_affine() returns true it'd be (this) 'cpu'. I cannot see where the prev_cpu or the cpu is set to another one before calling select_idle_sibling. Thanks, Namhyung