From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932342AbVKKEIN (ORCPT ); Thu, 10 Nov 2005 23:08:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932343AbVKKEIN (ORCPT ); Thu, 10 Nov 2005 23:08:13 -0500 Received: from ms-smtp-04.nyroc.rr.com ([24.24.2.58]:38042 "EHLO ms-smtp-04.nyroc.rr.com") by vger.kernel.org with ESMTP id S932342AbVKKEIN (ORCPT ); Thu, 10 Nov 2005 23:08:13 -0500 Subject: Re: Update on Timer Frequencies From: Steven Rostedt To: AndyLiebman@aol.com Cc: linux-kernel@vger.kernel.org In-Reply-To: <1131597313.14381.234.camel@localhost.localdomain> References: <206.db80c15.30a174f6@aol.com> <1131422329.14381.157.camel@localhost.localdomain> <1131597313.14381.234.camel@localhost.localdomain> Content-Type: text/plain Organization: Kihon Technologies Date: Thu, 10 Nov 2005 23:08:08 -0500 Message-Id: <1131682088.10894.9.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2005-11-09 at 23:35 -0500, Steven Rostedt wrote: > On Mon, 2005-11-07 at 22:58 -0500, Steven Rostedt wrote: > > > > Running my logdev tools from: > http://www.kihontech.com/logdev/logdev_tools_0.3.0.tar.bz2 > > ./logread /dev/logdev > 1000HZ.out # with 1000HZ > ./logread /dev/logdev > 100HZ.out # with 100HZ > > These files can be found at: > http://www.kihontech.com/tests/hz_times/ > > These show all the times that a context switch took place. This is a > ring buffer, so it only captured the last 30 some seconds of the test. > But that should be good enough. > > with my analyze.pl script (also supplied at the website) I ran: > > ./analyze.pl 1000HZ.out > 1000HZ.txt > and again for 100HZ. > > This calculates the times between the context switches and at the end > produces an average. > > (all times are in seconds) > > For 100HZ: > > [54543.530810] CPU:0 (testme:2539) -->> (find:2550) > diff: 0.000213 > [54543.546730] CPU:0 (find:2550) -->> (testme:2539) > diff: 0.015920 > count: 28974 total: 38.384180 > average: 0.001325 The above 100HZ test is invalid. As shown in the times, it was run after 54000 some seconds, which means that the file system was probably already cached. So I did fresh reboots and ran the test shortly after bootup. The test results are again at http://www.kihontech.com/tests/hz_times/ but they are all with a *_2.* in the name. Here are the times that were run for each test (100HZ vs 1000HZ and preempt vs nopreempt). 1000HZ preempt: Thu Nov 10 18:05:11 EST 2005 Thu Nov 10 18:13:01 EST 2005 real 7m49.741s user 0m46.464s sys 4m41.524s 1000HZ nopreempt: Thu Nov 10 22:17:33 EST 2005 Thu Nov 10 22:25:15 EST 2005 real 7m42.339s user 0m47.156s sys 4m33.205s 100HZ preempt: # time ./testme Thu Nov 10 17:40:29 EST 2005 Thu Nov 10 17:48:12 EST 2005 real 7m42.418s user 0m46.190s sys 4m40.350s 100HZ nopreempt: Thu Nov 10 17:52:15 EST 2005 Thu Nov 10 17:59:56 EST 2005 real 7m40.976s user 0m44.840s sys 4m34.510s This seems to show that 100HZ with no preemption was the fastest, but the times are too close, so it is of a difference of ~0.2% which is well in the margin of error. So this test really doesn't show much benefit between the settings. Tomorrow, I'll see if I can make a test that serves up web pages, and see if that will show the benefits for servers and the settings for HZ and preemption. -- Steve