From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: Git and GCC Date: Fri, 7 Dec 2007 09:23:47 -0800 (PST) Message-ID: References: <20071206.193121.40404287.davem@davemloft.net> <20071207063848.GA13101@coredump.intra.peff.net> <9e4733910712062310s30153afibc44a5550fd9ea99@mail.gmail.com> <20071207.045329.204650714.davem@davemloft.net> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: jonsmirl@gmail.com, peff@peff.net, nico@cam.org, dberlin@dberlin.org, harvey.harrison@gmail.com, ismail@pardus.org.tr, gcc@gcc.gnu.org, git@vger.kernel.org To: David Miller X-From: gcc-return-142810-gcc=m.gmane.org@gcc.gnu.org Fri Dec 07 18:25:15 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 1J0gwq-00035h-6b for gcc@gmane.org; Fri, 07 Dec 2007 18:25:12 +0100 Received: (qmail 15044 invoked by alias); 7 Dec 2007 17:24:53 -0000 Received: (qmail 15035 invoked by uid 22791); 7 Dec 2007 17:24:52 -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; Fri, 07 Dec 2007 17:24:08 +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 lB7HNn1o031890 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 7 Dec 2007 09:23:50 -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 lB7HNlmN027780; Fri, 7 Dec 2007 09:23:48 -0800 In-Reply-To: <20071207.045329.204650714.davem@davemloft.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 Fri, 7 Dec 2007, David Miller wrote: > > Also I could end up being performance limited by SHA, it's not very > well tuned on Sparc. It's been on my TODO list to code up the crypto > unit support for Niagara-2 in the kernel, then work with Herbert Xu on > the userland interfaces to take advantage of that in things like > libssl. Even a better C/asm version would probably improve GIT > performance a bit. I doubt yu can use the hardware support. Kernel-only hw support is inherently broken for any sane user-space usage, the setup costs are just way way too high. To be useful, crypto engines need to support direct user space access (ie a regular instruction, with all state being held in normal registers that get saved/restored by the kernel). > Is SHA a significant portion of the compute during these repacks? > I should run oprofile... SHA1 is almost totally insignificant on x86. It hardly shows up. But we have a good optimized version there. zlib tends to be a lot more noticeable (especially the uncompression: it may be faster than compression, but it's done _so_ much more that it totally dominates). Linus