From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: Git and GCC Date: Thu, 6 Dec 2007 10:35:22 -0800 (PST) Message-ID: References: <4aca3dc20712051947t5fbbb383ua1727c652eb25d7e@mail.gmail.com> <20071205.202047.58135920.davem@davemloft.net> <4aca3dc20712052032n521c344cla07a5df1f2c26cb8@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> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Nicolas Pitre , Jon Smirl , Daniel Berlin , Harvey Harrison , David Miller , ismail@pardus.org.tr, gcc@gcc.gnu.org, git@vger.kernel.org To: Jeff King X-From: gcc-return-142757-gcc=m.gmane.org@gcc.gnu.org Thu Dec 06 19:36:30 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 1J0La7-00076o-TE for gcc@gmane.org; Thu, 06 Dec 2007 19:36:20 +0100 Received: (qmail 30735 invoked by alias); 6 Dec 2007 18:36:01 -0000 Received: (qmail 30720 invoked by uid 22791); 6 Dec 2007 18:36:01 -0000 X-Spam-Check-By: sourceware.org Received: from smtp2.linux-foundation.org (HELO smtp2.linux-foundation.org) (207.189.120.14) by sourceware.org (qpsmtpd/0.31) with ESMTP; Thu, 06 Dec 2007 18:35:54 +0000 Received: from imap1.linux-foundation.org (imap1.linux-foundation.org [207.189.120.55]) by smtp2.linux-foundation.org (8.13.5.20060308/8.13.5/Debian-3ubuntu1.1) with ESMTP id lB6IZO9u022958 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 6 Dec 2007 10:35:25 -0800 Received: from localhost (localhost [127.0.0.1]) by imap1.linux-foundation.org (8.13.5.20060308/8.13.5/Debian-3ubuntu1.1) with ESMTP id lB6IZMv2005873; Thu, 6 Dec 2007 10:35:23 -0800 In-Reply-To: <20071206173946.GA10845@sigill.intra.peff.net> X-MIMEDefang-Filter: lf$Revision: 1.188 $ 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, 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?) Linus