From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1LRpQa-000431-Ca
	for qemu-devel@nongnu.org; Tue, 27 Jan 2009 10:00:36 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1LRpQZ-00041X-2j
	for qemu-devel@nongnu.org; Tue, 27 Jan 2009 10:00:35 -0500
Received: from [199.232.76.173] (port=44342 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1LRpQY-00041F-OB
	for qemu-devel@nongnu.org; Tue, 27 Jan 2009 10:00:34 -0500
Received: from ey-out-1920.google.com ([74.125.78.149]:12449)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <laurent.desnogues@gmail.com>) id 1LRpQY-0004Ol-7U
	for qemu-devel@nongnu.org; Tue, 27 Jan 2009 10:00:34 -0500
Received: by ey-out-1920.google.com with SMTP id 26so788778eyw.4
	for <qemu-devel@nongnu.org>; Tue, 27 Jan 2009 07:00:32 -0800 (PST)
MIME-Version: 1.0
In-Reply-To: <497ED233.7010504@suse.de>
References: <1232826287-18542-1-git-send-email-agraf@suse.de>
	<200901270034.04844.paul@codesourcery.com>
	<20090127004232.GE9296@shareable.org>
	<200901270059.21958.paul@codesourcery.com>
	<497E61DE.2080802@us.ibm.com> <497ED233.7010504@suse.de>
Date: Tue, 27 Jan 2009 16:00:32 +0100
Message-ID: <761ea48b0901270700g208c28b1r3c57f0f3c59d109c@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X
From: Laurent Desnogues <laurent.desnogues@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: qemu-devel@nongnu.org

On Tue, Jan 27, 2009 at 10:21 AM, Alexander Graf <agraf@suse.de> wrote:
>
> The extra registers should speed up things quite a bit. While that's not
> too much of a problem when emulating x86, which has few registers
> anyway, emulating a ppc or x86_64 target should be faster on an x86_64
> host. I haven't done measurements though.
>
> As for the plus in code size on x86_64 - that doesn't really apply to
> tcg, as that still generates 32-bit code when only 32-bit code is
> necessary, which still looks the same on x86_64. Plus it does simplify
> 64-bit operations.
>
> I would be very surprised if the improvement of emulating x86_64 on x86
> vs. x86_64 is only ~10%.

Here is a quick result for user mode.

x on y means running an target x on host y (the host is the same,
I just forced --cpu=i386 when compiling qemu).

Host:  CentOS 5.2 x86_64, E6600 (2.4GHz)
Benchmark: Spec2k gcc/integrate (compiled with gcc 4.1.2 -O2)

i386 on x86_64
gen code size       4005696/33497088
TB count            30704/524288
real    0m24.983s/user    0m24.834s

x86_64 on x86_64
gen code size       4413408/33497088
TB count            30247/524288
real    0m24.932s/user    0m24.749s

i386 on i386
gen code size       3439008/33497088
TB count            30704/524288
real    0m26.391s/user    0m26.131s

x86_64 on i386
gen code size       5715248/33497088
TB count            30254/524288
real    0m28.233s/user    0m27.985s


Laurent