From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753774AbaE1BGi (ORCPT ); Tue, 27 May 2014 21:06:38 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:22678 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753543AbaE1BGh (ORCPT ); Tue, 27 May 2014 21:06:37 -0400 Message-ID: <5385368E.2060507@huawei.com> Date: Wed, 28 May 2014 09:06:22 +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: Thomas Gleixner CC: Mike Galbraith , , LKML , Greg KH , "Li Zefan" , , Huang Qiang 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> <53844510.1040502@huawei.com> <1401184553.5134.115.camel@marge.simpson.net> <53848A2C.5010209@huawei.com> In-Reply-To: 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 2014/5/28 4:53, Thomas Gleixner wrote: > On Tue, 27 May 2014, Libo Chen wrote: >> On 2014/5/27 17:55, Mike Galbraith wrote: >>> On Tue, 2014-05-27 at 15:56 +0800, Libo Chen wrote: >>>>> 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. >>> Something is rotten. 3.14-rt contains that commit, I ran your test with >>> 256 threads on 64 core box, saw ~4%. >>> >>> Putting master/nopreempt config on box and doing the same test, box is >>> chewing up truckloads of CPU, but not from migrations. >>> >>> perf top -g --sort=symbol >> in my box: >> >> perf top -g --sort=symbol >> >> Events: 3K cycles >> 73.27% [k] read_hpet > > Why is that machine using read_hpet() ? > > Please provide the output of > > # dmesg | grep -i tsc > Euler:/home # dmesg | grep -i tsc [ 0.000000] Fast TSC calibration using PIT [ 0.226921] TSC synchronization [CPU#0 -> CPU#1]: [ 0.227142] Measured 1053728 cycles TSC warp between CPUs, turning off TSC clock. [ 0.008000] Marking TSC unstable due to check_tsc_sync_source failed > and > > # cat /sys/devices/system/clocksource/clocksource0/available_clocksource hpet acpi_pm > > and > > # cat /sys/devices/system/clocksource/clocksource0/current_clocksource hpet > > Thanks, > > tglx > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > > . >