From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22200 invoked by alias); 21 Jul 2005 13:03:19 -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 22168 invoked by uid 22791); 21 Jul 2005 13:03:15 -0000 Received: from atrey.karlin.mff.cuni.cz (HELO atrey.karlin.mff.cuni.cz) (195.113.31.123) by sourceware.org (qpsmtpd/0.30-dev) with ESMTP; Thu, 21 Jul 2005 13:03:15 +0000 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 4018) id A19C64B43FC; Thu, 21 Jul 2005 15:02:24 +0200 (CEST) Date: Thu, 21 Jul 2005 13:03:00 -0000 From: Jan Hubicka To: girish vaitheeswaran Cc: Jan Hubicka , Janis Johnson , gcc@gcc.gnu.org Subject: Re: -fprofile-generate and -fprofile-use Message-ID: <20050721130224.GA7310@atrey.karlin.mff.cuni.cz> References: <20050720224416.GA13654@atrey.karlin.mff.cuni.cz> <20050720233834.30683.qmail@web80006.mail.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050720233834.30683.qmail@web80006.mail.yahoo.com> User-Agent: Mutt/1.5.6+20040907i X-SW-Source: 2005-07/txt/msg00899.txt.bz2 > I started with a clean slate in my build environment > and did not have any residual files hanging around. > Are the steps I have indicated in my earlier email > correct. Is there a way I can break down the problem > into a smaller sub-set of flags and eliminate the flag > causing the performance problem. What I mean is since > -fprofile-generate and -fprofile-use enable a bunch of > flags, would it make sense to avoid profiling and try > out some of the individual flags on a trial and error > basis. If so what would be the flags to start the It would be probably better to just turn off the individual optimizations with -fprofile-use (for optimizations that are implied by this flag there should be no need to re-profile each time). If you can find particular optimization that gets out of control, it would be lot easier to fix it... Honza > trials with. > > -girish > > --- Jan Hubicka wrote: > > > > On Wed, Jul 20, 2005 at 10:45:01AM -0700, girish > > vaitheeswaran wrote: > > > > > --- Steven Bosscher wrote: > > > > > > > > > > > On Wednesday 20 July 2005 18:53, girish > > vaitheeswaran wrote: > > > > > > > I am seeing a 20% slowdown with feedback > > optimization. > > > > > > > Does anyone have any thoughts on this. > > > > > > > > > > > > My first thought is that you should probably > > first > > > > > > tell what compiler > > > > > > you are using. > > > > > > > > I am using gcc 3.4.3 > > > > -girish > > > > > > Which platform? I've seen slower code for > > profile-directed optimizations > > > on powerpc64-linux with GCC 4.0 and mainline. > > It's a bug, but I haven't > > > looked into it enough to provide a small test case > > for a problem report. > > > > Actually I would be very interested in seeing > > testcases such as those. > > (and the Girish' slowdown too if possible). In > > general some slowdowns > > in side corners are probably unavoidable but both > > 3.4.3 and 4.0 seems to > > have pretty consistent improvements with profiling > > at least for SPEC and > > i386 I am testing pretty regularly. > > Such slodowns usually indicate problems like > > incorrectly updated profile > > or incorrectly readed in profile because of > > missmatch in CFGs in between > > profile and feedback run that are rather dificult to > > notice and hunt > > down... > > > > Honza > > > > > > Janis > >