From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2099 invoked by alias); 2 Aug 2011 05:48:35 -0000 Received: (qmail 2089 invoked by uid 22791); 2 Aug 2011 05:48:33 -0000 X-SWARE-Spam-Status: No, hits=-2.7 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,RP_MATCHES_RCVD,SPF_HELO_PASS X-Spam-Check-By: sourceware.org Received: from smtp-out.google.com (HELO smtp-out.google.com) (74.125.121.67) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 02 Aug 2011 05:48:19 +0000 Received: from kpbe16.cbf.corp.google.com (kpbe16.cbf.corp.google.com [172.25.105.80]) by smtp-out.google.com with ESMTP id p725mHw0031975 for ; Mon, 1 Aug 2011 22:48:17 -0700 Received: from gwb17 (gwb17.prod.google.com [10.200.2.17]) by kpbe16.cbf.corp.google.com with ESMTP id p725m5ah017673 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Mon, 1 Aug 2011 22:48:16 -0700 Received: by gwb17 with SMTP id 17so4549245gwb.29 for ; Mon, 01 Aug 2011 22:48:15 -0700 (PDT) MIME-Version: 1.0 Received: by 10.150.103.1 with SMTP id a1mr1458120ybc.244.1312264095776; Mon, 01 Aug 2011 22:48:15 -0700 (PDT) Received: by 10.151.101.7 with HTTP; Mon, 1 Aug 2011 22:48:15 -0700 (PDT) In-Reply-To: <4E36F3BD.9080804@riverbed.com> References: <4E32F44F.7090201@riverbed.com> <4E330282.5000303@riverbed.com> <4E36F3BD.9080804@riverbed.com> Date: Tue, 02 Aug 2011 05:48:00 -0000 Message-ID: Subject: Re: Performance degradation on g++ 4.6 From: Xinliang David Li To: Oleg Smolsky Cc: gcc@gcc.gnu.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-System-Of-Record: true X-IsSubscribed: yes Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org X-SW-Source: 2011-08/txt/msg00032.txt.bz2 Try isolate the int8_t constant folding testing from the rest to see if the slow down can be reproduced with the isolated case. If the problem disappear, it is likely due to the following inline parameters: large-function-insns, large-function-growth, large-unit-insns, inline-unit-growth. For instance set --param large-function-insns=3D10000 --param large-unit-insns=3D20000 David On Mon, Aug 1, 2011 at 11:43 AM, Oleg Smolsky w= rote: > On 2011/7/29 14:07, Xinliang David Li wrote: >> >> Profiling tools are your best friend here. If you don't have access to >> any, the least you can do is to build the program with -pg option and >> use gprof tool to find out differences. > > The test suite has a bunch of very basic C++ tests that are executed an > enormous number of times. I've built one with the obvious performance > degradation and attached the source, output and reports. > > Here are some highlights: > =A0 =A0v4.1: =A0 =A0Total absolute time for int8_t constant folding: 30.4= 2 sec > =A0 =A0v4.6: =A0 =A0Total absolute time for int8_t constant folding: 43.3= 2 sec > > Every one of the tests in this section had degraded... the first half more > than the second. I am not sure how much further I can take this - the > benchmarked code is very short and plain. I can post disassembly for one > (some?) of them if anyone is willing to take a look... > > Thanks, > Oleg. >