From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Pitre Subject: Re: Git and GCC Date: Thu, 06 Dec 2007 14:08:12 -0500 (EST) Message-ID: References: <4aca3dc20712051947t5fbbb383ua1727c652eb25d7e@mail.gmail.com> <20071205.204848.227521641.davem@davemloft.net> <4aca3dc20712052111o730f6fb6h7a329ee811a70f28@mail.gmail.com> <1196918132.10408.85.camel@brick> <4aca3dc20712052117j3ef5cf99y848d4962ae8ddf33@mail.gmail.com> <9e4733910712052247x116cabb4q48ebafffb93f7e03@mail.gmail.com> <20071206071503.GA19504@coredump.intra.peff.net> <20071206173946.GA10845@sigill.intra.peff.net> <9e4733910712061055p353775d8wd0321bc9c81297b7@mail.gmail.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Transfer-Encoding: 7BIT Cc: Linus Torvalds , Jeff King , Daniel Berlin , Harvey Harrison , David Miller , ismail@pardus.org.tr, gcc@gcc.gnu.org, git@vger.kernel.org To: Jon Smirl X-From: gcc-return-142761-gcc=m.gmane.org@gcc.gnu.org Thu Dec 06 20:09:21 2007 Return-path: Envelope-to: gcc@gmane.org Received: from sourceware.org ([209.132.176.174]) by lo.gmane.org with smtp (Exim 4.50) id 1J0M61-0004IO-1o for gcc@gmane.org; Thu, 06 Dec 2007 20:09:17 +0100 Received: (qmail 25737 invoked by alias); 6 Dec 2007 19:08:58 -0000 Received: (qmail 25722 invoked by uid 22791); 6 Dec 2007 19:08:57 -0000 X-Spam-Check-By: sourceware.org Received: from relais.videotron.ca (HELO relais.videotron.ca) (24.201.245.36) by sourceware.org (qpsmtpd/0.31) with ESMTP; Thu, 06 Dec 2007 19:08:51 +0000 Received: from xanadu.home ([74.56.106.175]) by VL-MO-MR004.ip.videotron.ca (Sun Java(tm) System Messaging Server 6.3-4.01 (built Aug 3 2007; 32bit)) with ESMTP id <0JSN00FLX6HOWH30@VL-MO-MR004.ip.videotron.ca> for gcc@gcc.gnu.org; Thu, 06 Dec 2007 14:08:12 -0500 (EST) In-reply-to: <9e4733910712061055p353775d8wd0321bc9c81297b7@mail.gmail.com> User-Agent: Alpine 0.99999 (LFD 814 2007-11-14) Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Delivered-To: mailing list gcc@gcc.gnu.org Archived-At: On Thu, 6 Dec 2007, Jon Smirl wrote: > On 12/6/07, Linus Torvalds wrote: > > > > > > On Thu, 6 Dec 2007, Jeff King wrote: > > > > > > What is really disappointing is that we saved only about 20% of the > > > time. I didn't sit around watching the stages, but my guess is that we > > > spent a long time in the single threaded "writing objects" stage with a > > > thrashing delta cache. > > > > I don't think you spent all that much time writing the objects. That part > > isn't very intensive, it's mostly about the IO. > > > > I suspect you may simply be dominated by memory-throughput issues. The > > delta matching doesn't cache all that well, and using two or more cores > > isn't going to help all that much if they are largely waiting for memory > > (and quite possibly also perhaps fighting each other for a shared cache? > > Is this a Core 2 with the shared L2?) > > When I lasted looked at the code, the problem was in evenly dividing > the work. I was using a four core machine and most of the time one > core would end up with 3-5x the work of the lightest loaded core. > Setting pack.threads up to 20 fixed the problem. With a high number of > threads I was able to get a 4hr pack to finished in something like > 1:15. But as far as I know you didn't try my latest incarnation which has been available in Git's master branch for a few months already. Nicolas