From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35364) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCT19-0002WN-6P for qemu-devel@nongnu.org; Fri, 14 Sep 2012 06:21:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TCT0z-0006q3-FL for qemu-devel@nongnu.org; Fri, 14 Sep 2012 06:20:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62330) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCT0z-0006pt-24 for qemu-devel@nongnu.org; Fri, 14 Sep 2012 06:20:49 -0400 Date: Fri, 14 Sep 2012 11:20:44 +0100 From: "Daniel P. Berrange" Message-ID: <20120914102044.GL6819@redhat.com> References: <5052DF3A.1070007@msgid.tls.msk.ru> <20120914093304.GC6819@redhat.com> <5052FB60.3060109@msgid.tls.msk.ru> <50530047.9030703@siemens.com> <5053010E.1000103@msgid.tls.msk.ru> <5053031B.8020902@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5053031B.8020902@siemens.com> Subject: Re: [Qemu-devel] qemu-system-i386 vs qemu-system-x86_64 ? Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Michael Tokarev , qemu-devel On Fri, Sep 14, 2012 at 12:12:43PM +0200, Jan Kiszka wrote: > On 2012-09-14 12:03, Michael Tokarev wrote: > > On 14.09.2012 14:00, Jan Kiszka wrote: > > [] > >> The major difference in qemu-system-i386 vs. qemu-system-x86_64 is on > >> the TCG side: We measured noticeable performance benefits when running > >> 32/16 bit OSes against qemu-system-i386 vs. using qemu-system-x86_64. I > >> don't have numbers at hand, but colleagues decided to use the 32-bit > >> version for that reason (when no KVM is available). > > > > Interesting. Maybe someone should look at the difference on TCG side > > and merge interesting bits from i386 to x86_64... :) > > I suppose the difference - for our use cases at least - lies in the > different register and address sizes. Maybe there is room for more > runtime optimizations, we never looked in that details as -i386 still > works fine. And, if you are on 32-bit host (see below) - but we aren't, > qemu-system-x86_64 hurts even more. > > > > > The thing is: x86_64 becomes the only x86 platform these days, or at > > least the MAIN platform. > > I know, and I'm telling everyone. Still, too many crazy people keep on > installing 32-bit distros or even 32-bit kernels. Maybe x64-32 will > improve this. It is quite depressing that 32-bit still accounts for 55% of deployed Fedora installs: http://smolt.fedoraproject.org/static/stats/stats.html That said, a year ago it was even worse with 32-bit up in 70% region Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|