From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31106 invoked by alias); 3 Feb 2011 20:52:48 -0000 Received: (qmail 31098 invoked by uid 22791); 3 Feb 2011 20:52:47 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=BAYES_00 X-Spam-Check-By: sourceware.org Received: from zwopi.com (HELO daffy.zwopi.com) (85.214.124.126) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 03 Feb 2011 20:52:41 +0000 Received: by daffy.zwopi.com (Postfix, from userid 80) id 0CD4A85; Thu, 3 Feb 2011 21:52:38 +0100 (CET) To: Michael Snyder Subject: Re: performance of multithreading gets gradually worse under gdb X-PHP-Originating-Script: 0:func.inc MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 03 Feb 2011 20:52:00 -0000 From: Markus Alber Cc: In-Reply-To: <4D4B0F71.1020708@vmware.com> References: <8b62d2819c94a232987155aa99e01983@hyperion-imrt.org> <4D49BE4E.9000009@vmware.com> <76bccf1875854ebc69b6a892fb84a976@hyperion-imrt.org> <4D49D016.7000607@vmware.com> <0e69c90ce85e34a24a5bcef1ce391aae@hyperion-imrt.org> <4D4B0F71.1020708@vmware.com> Message-ID: <38fe09dafa0e58ac3327f41b3afed1ed@hyperion-imrt.org> X-Sender: markus@hyperion-imrt.org User-Agent: Roundcube Webmail/0.5 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org X-SW-Source: 2011-02/txt/msg00017.txt.bz2 On Thu, 03 Feb 2011 12:26:25 -0800, Michael Snyder wrote: > Markus Alber wrote: >> I compiled gdb-6.5 alright and it performs well as usual, without >> this problem. > > Good info. What version of gdb were you using when you detected the > problem? it was gdb 7.1 as it comes with OpenSuSE 11.3 Meanwhile I tried every release between 6.5 and 7.2. All the 7's showed the problem, but it was also perceivable with 6.8.91. I was a bit too quick to assert that 6.5 was working well... it wasn't possible to set break points, some 6.8 versions crashed. There seems to be some incompatibility between the compiler on OpenSuse 11.3 and the older gdbs (I got them as sources from the gnu repository) > I ran your program stand-alone, then under gdb 7.0, then gdb 7.2CVS. > On my not-so-new system I got the following times: > stand alone: 15m33s > gdb 7.0 16m > gdb 7.2CVS 16m10s So I presume the stripping-down removed something that causes the problem in the larger application. Or, is it a possibility that it has something to do with the kernel or compiler of OpenSuSE 11.3? Meanwhile I've gone back to my older 4-core machine running gdb 6.5 on OpenSuse 10.2. Performance is constant throughout. I did notice that gdb allocates memory for each iteration. > > I could not perceive any change in the cycle time from beginning to > end. > > GDB 7.0 did increase its memory footprint by about 3mb during the run > (3 percent). So that could indicate some leakage, around 15k per > cycle. > But I can't see that as the main reason for the slow-down you're > reporting, considering that your system is not memory bound. > > GDB 7.2CVS increased its memory footprint by only about 500kb during > the > whole run, so you might consider giving that a try. Instructions for > getting the latest development sources are here: > > http://sourceware.org/gdb/current/ > > If you'd be willing to contribute your little sample program, we > might be able to use it for a thread debugging stress test or > something. > > Michael