From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752459Ab3BEHWb (ORCPT ); Tue, 5 Feb 2013 02:22:31 -0500 Received: from forward17.mail.yandex.net ([95.108.253.142]:42240 "EHLO forward17.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751137Ab3BEHW3 (ORCPT ); Tue, 5 Feb 2013 02:22:29 -0500 From: Kirill Tkhai To: Honghui Zhang Cc: Steven Rostedt , linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , linux-rt-users Subject: Re:[PATCH] sched/rt: Decrease number of calls of push_rt_task() in push_rt_tasks() MIME-Version: 1.0 Message-Id: <500221360048944@web26g.yandex.ru> X-Mailer: Yamail [ http://yandex.ru ] 5.0 Date: Tue, 05 Feb 2013 11:22:24 +0400 Content-Transfer-Encoding: 7bit Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On 2013/2/1 5:57, Kirill Tkhai wrote: > >> 31.01.2013, 20:08, "Steven Rostedt" : >> >>> On Mon, 2013-01-28 at 03:46 +0400, Kirill Tkhai wrote: >>> >>>> The patch aims to decrease the number of calls of push_rt_task() >>>> in push_rt_tasks(). >>>> >>>> It's not necessary to push more than 'num_online_cpus() - 1' tasks. >>>> If just pushed task doesn't leave its new CPU during our local call >>>> of push_rt_tasks() than we won't push another task to the CPU. >>>> If it leave or change priority than it will pull new task by itself. >>> >>> I'm curious. Have you hit situations where this was an issue? Or was >>> this just discovered by code review? >> >> No, I did't hit this situation. It's impossible to hook every situation. >> >> Thanks for your explanation. >> >> Kirill > > Suppose we have a large number of cpus(say 4096), with the last one running > a low-priority task on it. Is it possible with this patch we will never reach > the last cpu in case that previous cpu has complete the pulled task? Yes. But this patch is about several pushable tasks on the same cpu. Kirill --