From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752098AbaE0H5H (ORCPT ); Tue, 27 May 2014 03:57:07 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:25417 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752022AbaE0H5D (ORCPT ); Tue, 27 May 2014 03:57:03 -0400 Message-ID: <53844510.1040502@huawei.com> Date: Tue, 27 May 2014 15:56:00 +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: Mike Galbraith CC: , , LKML , Greg KH , "Li Zefan" , Subject: Re: balance storm References: <5382AF2E.1040407@huawei.com> <1401081082.5339.41.camel@marge.simpson.net> <538330B7.5070503@huawei.com> <1401113960.23186.41.camel@marge.simpson.net> In-Reply-To: <1401113960.23186.41.camel@marge.simpson.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 2014/5/26 22:19, Mike Galbraith wrote: > On Mon, 2014-05-26 at 20:16 +0800, Libo Chen wrote: >> On 2014/5/26 13:11, Mike Galbraith wrote: > >>> Your synthetic test is the absolute worst case scenario. There has to >>> be work between wakeups for select_idle_sibling() to have any chance >>> whatsoever of turning in a win. At 0 work, it becomes 100% overhead. >> >> not synthetic, it is a real problem in our product. under no load, waste >> much cpu time. > > What happens in your product if you apply the commit I pointed out? under no load, cpu usage is up to 60%, but the same apps cost 10% on susp sp1. The apps use a lot of timer. I am not sure that commit is the root cause, but they do have some different cpu usage between 3.4.24 and suse sp1, e.g. my synthetic test before. > >>>> so I think 15% cpu usage and migration event are too high, how to fixed? >>> >>> You can't for free, low latency wakeup can be worth one hell of a lot. >>> >>> You could do a decayed hit/miss or such to shut the thing off when the >>> price is just too high. Restricting migrations per unit time per task >>> also helps cut the cost, but hurts tasks that could have gotten to the >>> CPU quicker, and started your next bit of work. Anything you do there >>> is going to be a rob Peter to pay Paul thing. >>> >> >> I had tried to change sched_migration_cost and sched_nr_migrate in /proc, >> but no use. any other suggestion? >> >> I still think this is a problem to schedular. it is better to directly solve >> this issue instead of a workaroud > > I didn't say it wasn't a problem, it is. I said whatever you do will be > a tradeoff. > > -Mike > > >