From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752103AbaE0M4T (ORCPT ); Tue, 27 May 2014 08:56:19 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:30055 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751869AbaE0M4S (ORCPT ); Tue, 27 May 2014 08:56:18 -0400 Message-ID: <53848B38.5090408@huawei.com> Date: Tue, 27 May 2014 20:55:20 +0800 From: Libo Chen User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Peter Zijlstra CC: Mike Galbraith , , , LKML , Greg KH , Li Zefan Subject: Re: balance storm References: <5382AF2E.1040407@huawei.com> <1401090987.5339.79.camel@marge.simpson.net> <53832A36.5020205@huawei.com> <20140527094802.GN30445@twins.programming.kicks-ass.net> In-Reply-To: <20140527094802.GN30445@twins.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.22.241] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/5/27 17:48, Peter Zijlstra wrote: > So: > > 1) what kind of weird ass workload is that? Why are you waking up so > often to do no work? it's just a testcase, I agree it doesn`t exist in real world. > > 2) turning on/off share_pkg_resource is a horrid hack whichever way > aruond you turn it. > > So I suppose this is due to the select_idle_sibling() nonsense again, > where we assumes L3 is a fair compromise between cheap enough and > effective enough. > > Of course, Intel keeps growing the cpu count covered by L3 to ridiculous > sizes, 8 cores isn't nowhere near their top silly, which shifts the > balance, and there's always going to be pathological cases (like the > proposed workload) where its just always going to suck eggs. > > Also, when running 50 such things on a 16 cpu machine, you get roughly 3 > per cpu, since their runtime is stupid low, I would expect it to pretty > much always hit an idle cpu, which in turn should inhibit the migration. > > Then again, maybe the timer slack is causing you grief, resulting in all > 3 being woken at the same time, instead of having them staggered. > > In any case, I'm not sure what the 'regression' report is against, as > there's only a single kernel version mentioned: 3.4, and that's almost a upstream has the same problem, I have mentioned before. > dinosaur.