From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Lnija-0002S9-3q for qemu-devel@nongnu.org; Sat, 28 Mar 2009 20:18:42 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LnijV-0002Pg-Om for qemu-devel@nongnu.org; Sat, 28 Mar 2009 20:18:41 -0400 Received: from [199.232.76.173] (port=36341 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LnijV-0002PZ-Bk for qemu-devel@nongnu.org; Sat, 28 Mar 2009 20:18:37 -0400 Received: from mx20.gnu.org ([199.232.41.8]:13043) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LnijV-0005qT-2R for qemu-devel@nongnu.org; Sat, 28 Mar 2009 20:18:37 -0400 Received: from mail.codesourcery.com ([65.74.133.4]) by mx20.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LnijT-0001v1-Kg for qemu-devel@nongnu.org; Sat, 28 Mar 2009 20:18:36 -0400 Date: Sat, 28 Mar 2009 17:18:34 -0700 From: Nathan Froyd Subject: Re: [Qemu-devel] [PATCH 0/4] target-ppc: create TCG slots for registers based on CPU Message-ID: <20090329001834.GK7336@codesourcery.com> References: <1238275817-9758-1-git-send-email-froydnj@codesourcery.com> <20090328225443.GL20944@hall.aurel32.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090328225443.GL20944@hall.aurel32.net> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org On Sat, Mar 28, 2009 at 11:54:43PM +0100, Aurelien Jarno wrote: > On Sat, Mar 28, 2009 at 02:30:13PM -0700, Nathan Froyd wrote: > > I am not a TCG expert, but there are several loops in TCG over all > > globals and it seems like those loops would go faster if they didn't > > have to consider registers that would never be touched. If this patch > > series makes no difference in TCG's performance, then I'd be glad to > > have an explanation of why that's the case. > > Do you actually have run a benchmark with those changes? TCG is > sometimes a bit strange, and some optimizations does not change the > execution speed, while others improve it a lot. It is very difficult to > predict what will give a gain or not. > > Suggestions of benchmarks: gzip/bzip2 on a big file using user emulation > or a compilation in system emulation. Benchmarking? Pffft. ;) A benchmarking session with qemu-ppc and bzip2/bunzip2 on ~400MB files and a 603e emulated CPU suggests that these changes are not terribly beneficial (maybe 1% improvement, if that). I don't imagine that a similarly stressful benchmark in system emulation would be much different. Consider the patch series withdrawn. -Nathan