From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:33949) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCTC8-0008RY-Oa for qemu-devel@nongnu.org; Fri, 14 Sep 2012 06:32:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TCTC7-0002FR-Gw for qemu-devel@nongnu.org; Fri, 14 Sep 2012 06:32:20 -0400 Received: from thoth.sbs.de ([192.35.17.2]:30671) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCTC7-0002FJ-7R for qemu-devel@nongnu.org; Fri, 14 Sep 2012 06:32:19 -0400 Message-ID: <505307B1.10408@siemens.com> Date: Fri, 14 Sep 2012 12:32:17 +0200 From: Jan Kiszka MIME-Version: 1.0 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> <20120914102044.GL6819@redhat.com> In-Reply-To: <20120914102044.GL6819@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] qemu-system-i386 vs qemu-system-x86_64 ? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Michael Tokarev , qemu-devel On 2012-09-14 12:20, Daniel P. Berrange wrote: > 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 There is a nice comment by Steven that I pinned on my wall, the last paragraph text-marked: http://lkml.indiana.edu/hypermail/linux/kernel/1206.1/00445.html. These days, I prefer to just point people to that printout instead of arguing. Didn't help yet, unfortunately, to convince our corporate VPN vendor to finally support 64-bit with his proprietary clients. Maybe because they didn't visit my office yet. The problem is also that some distros default the download to 32-bit when asking for a desktop, e.g. Ubuntu or OpenSUSE. Kudos to Fedora for not doing this. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux