Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753397AbcC1BIG (ORCPT <rfc822;w@1wt.eu>);
	Sun, 27 Mar 2016 21:08:06 -0400
Received: from szxga03-in.huawei.com ([119.145.14.66]:8054 "EHLO
	szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752445AbcC1BIE (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Sun, 27 Mar 2016 21:08:04 -0400
Subject: Re: [PATCH 3/5] perf core: Prepare writing into ring buffer from end
To: pi3orama <pi3orama@163.com>, Peter Zijlstra <peterz@infradead.org>
References: <1457949585-191064-1-git-send-email-wangnan0@huawei.com>
 <1457949585-191064-4-git-send-email-wangnan0@huawei.com>
 <20160323095007.GW6344@twins.programming.kicks-ass.net>
 <56F52E83.70409@huawei.com> <56F530C1.9010106@huawei.com>
 <56F547CC.5000408@huawei.com>
 <20160327152005.GU6356@twins.programming.kicks-ass.net>
 <73914DEA-D304-4997-9CEA-9689E3BAA7BE@163.com>
CC: <mingo@redhat.com>, <linux-kernel@vger.kernel.org>,
        He Kuang <hekuang@huawei.com>, Alexei Starovoitov <ast@kernel.org>,
        "Arnaldo Carvalho de Melo" <acme@redhat.com>,
        Brendan Gregg <brendan.d.gregg@gmail.com>,
        "Jiri Olsa" <jolsa@kernel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Namhyung Kim <namhyung@kernel.org>, Zefan Li <lizefan@huawei.com>
From: "Wangnan (F)" <wangnan0@huawei.com>
Message-ID: <56F883D4.6010406@huawei.com>
Date: Mon, 28 Mar 2016 09:07:32 +0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101
 Thunderbird/38.5.0
MIME-Version: 1.0
In-Reply-To: <73914DEA-D304-4997-9CEA-9689E3BAA7BE@163.com>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 8bit
X-Originating-IP: [10.111.66.109]
X-CFilter-Loop: Reflected
X-Mirapoint-Virus-RAPID-Raw: score=unknown(0),
	refid=str=0001.0A020201.56F883E7.0026,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0,
	ip=0.0.0.0,
	so=2013-05-26 15:14:31,
	dmn=2013-03-21 17:37:32
X-Mirapoint-Loop-Id: 9391db4aa22c80e2fb0d9f397f38fd66
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1617
Lines: 56



On 2016/3/27 23:30, pi3orama wrote:
>
> 发自我的 iPhone
>
>> 在 2016年3月27日，下午11:20，Peter Zijlstra <peterz@infradead.org> 写道：
>>
>> On Fri, Mar 25, 2016 at 10:14:36PM +0800, Wangnan (F) wrote:
>>>>> I think you enabled some unusual config options?
>> x86_64-defconfig
>>
>>>> You must enabled CONFIG_OPTIMIZE_INLINING. Now I get similar result:
>> It has that indeed.
>>
>>> After enabling CONFIG_OPTIMIZE_INLINING:
>>>
>>> Test its performance by calling 'close(-1)' for 3000000 times and
>>> use 'perf record -o /dev/null -e raw_syscalls:* test-ring-buffer' to
>>> capture system calls:
>>>
>>>                   MEAN         STDVAR
>>> BASE            800077.1     23448.13
>>> RAWPERF.PRE    2465858.0    603473.70
>>> RAWPERF.POST   2471925.0    609437.60
>>>
>>> Considering the high stdvar, after applying this patch the performance
>>> is not change.
>> Why is your variance so immense? And doesn't that render the
>> measurements pointless?
>>
> For some unknown reason, about
> 10% of these results raises 2 times of normal
> results. Say, "normal results" are about
> 2200000, but those "outliers" are about
> 4400000 (I can't access raw data now).
> Variance becomes much smaller if I remove
> those outliers.

After manually removing outliners (remove 10 outliners from 100 raw
data points in each data set):


                  MEAN         STDVAR
BASE            800077.1     23448.13
RAWPERF.PRE    2265741.0     10421.35
RAWPERF.POST   2269826.0     10507.45

Thank you.

> I guess the outliers is caused by some type
> of lock stepping? No clue about it.
>
> Thank you.
>