Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262937AbTHaWeG (ORCPT ); Sun, 31 Aug 2003 18:34:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262992AbTHaWeG (ORCPT ); Sun, 31 Aug 2003 18:34:06 -0400 Received: from rwcrmhc13.comcast.net ([204.127.198.39]:23193 "EHLO rwcrmhc13.comcast.net") by vger.kernel.org with ESMTP id S262937AbTHaWeD (ORCPT ); Sun, 31 Aug 2003 18:34:03 -0400 Message-ID: <3F527C63.7090805@kegel.com> Date: Sun, 31 Aug 2003 15:53:23 -0700 From: Dan Kegel User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030624 X-Accept-Language: de-de, en MIME-Version: 1.0 To: Larry McVoy CC: staelin@hpl.hp.com, linux-kernel@vger.kernel.org Subject: Re: LMbench as gcc performance regression test? References: <3F51A201.8090108@kegel.com> <20030831140037.GA16620@work.bitmover.com> <3F520773.1070907@kegel.com> <20030831145956.GE23783@work.bitmover.com> In-Reply-To: <20030831145956.GE23783@work.bitmover.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1807 Lines: 39 Larry McVoy wrote: > Here is some background, pick a benchmark and play with it and see if > you can convince yourself of anything. The basic idea is to run the > benchmark TRIES times for $ENOUGH milliseconds. TRIES is set to an odd > number in bench.h because we sort the results and take the midpoint and > print that as the result. It seems lat_pipe never does any median smoothing; it always sets TRIES to 1. However, at least on the fairly quiet embedded system I'm testing on, smoothing samples taken within a single run wouldn't make a huge difference. Any smoothing you get with that would be swamped by the fact that lat_pipe's result has a bimodal distribution only one of whose peaks shows up in any one run. This sure sounds like the kind of thing page coloring is supposed to solve; has anyone observed page coloring improving the repeatability of the lat_pipe benchmark? (There's no median smoothing in lat_pipe.c, I think, because it passes a value >= 1000000 as the 2nd arg of BENCH: BENCH(doit(p2[0], p1[1]), SHORT); BENCH computes the number of samples to take the median of as __N = (get_enough(1000000) <= 100000) ? TRIES : 1; get_enough() will always return at least what it is passed, thus __N will always be 1. It sure was whenever I printed it out, too. This seems to be the case for the following tests: bw_pipe bw_tcp bw_unix lat_fcntl lat_fifo lat_pipe lat_rpc lat_tcp lat_udp lat_unix) - Dan -- Dan Kegel http://www.kegel.com http://counter.li.org/cgi-bin/runscript/display-person.cgi?user=78045 - 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/