From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19126 invoked by alias); 22 Apr 2002 13:58:10 -0000 Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Received: (qmail 19098 invoked from network); 22 Apr 2002 13:58:04 -0000 Received: from unknown (HELO mail.alinoe.com) (24.132.80.10) by sources.redhat.com with SMTP; 22 Apr 2002 13:58:04 -0000 Received: (qmail 21770 invoked by uid 500); 22 Apr 2002 13:58:01 -0000 Date: Mon, 22 Apr 2002 07:11:00 -0000 From: Carlo Wood To: Michel LESPINASSE Cc: Jan Hubicka , Andreas Jaeger , gcc list Subject: Re: GCC performance regression - up to 20% ? Message-ID: <20020422155801.A21747@alinoe.com> References: <20020421005718.GA16378@zoy.org> <20020421113238.GC16602@atrey.karlin.mff.cuni.cz> <20020422061937.GA27171@zoy.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20020422061937.GA27171@zoy.org>; from walken@zoy.org on Sun, Apr 21, 2002 at 11:19:37PM -0700 X-SW-Source: 2002-04/txt/msg01081.txt.bz2 > > Then I tried to figure out where the slowdown is, using gprof. And > this is where things get really interesting: gprof tells me that the > code compiled with 3.1 is faster, but 'time' tells me that the user > time spent executing that code is higher with 3.1 than with 2.95. I'm > not sure what to make of this, but I think this might give you some > clues, so I'll describe it in more detail. I'm not sure what the > overhead is, but it seems to be right in gprof's blind spot. gprof "measures" the time that a function takes by probing which function the program is executing about every 20 ms. >From that it builds up a statistical histogram. I wish there would be a more precise profiler that uses the hardware counters. Does anyone know of one? Hmm, I remember a Subject: line on the PAPI mailinglist that mentioned gprof, but I deleted it. I think it asked the same question: whether or not there existed a 'gprof' that used PAPI. -- Carlo Wood