From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kirill Tkhai Subject: Re:[PATCH] sched/rt: Decrease number of calls of push_rt_task() in push_rt_tasks() Date: Tue, 05 Feb 2013 11:22:24 +0400 Message-ID: <500221360048944@web26g.yandex.ru> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Steven Rostedt , linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , linux-rt-users To: Honghui Zhang Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.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 --