From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=35541 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Pmkr0-0004q0-SN for qemu-devel@nongnu.org; Tue, 08 Feb 2011 05:31:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Pmkqz-0005x0-G5 for qemu-devel@nongnu.org; Tue, 08 Feb 2011 05:31:26 -0500 Received: from goliath.siemens.de ([192.35.17.28]:22003) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Pmkqz-0005wR-3r for qemu-devel@nongnu.org; Tue, 08 Feb 2011 05:31:25 -0500 Message-ID: <4D511B61.2060404@siemens.com> Date: Tue, 08 Feb 2011 11:30:57 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <4D3DFD20.8060004@linux.vnet.ibm.com> <20110125091741.GB30239@edde.se.axis.com> <20110125133453.GC5427@amt.cnet> <20110207101255.GA20413@amt.cnet> <20110207160350.GA26332@amt.cnet> <4D501C71.7090708@redhat.com> <4D50279B.5010102@siemens.com> <4D505DCB.9050406@codemonkey.ws> <20110207214551.GB16429@hall.aurel32.net> <4D50A5F0.802@codemonkey.ws> <20110208072657.GD16429@hall.aurel32.net> <4D50FA14.5010100@redhat.com> <4D5103E8.6050808@siemens.com> <4D510771.3040309@aurel32.net> <4D511221.9030505@siemens.com> <4D5113D3.9090802@aurel32.net> <4D511500.1040303@siemens.com> <4D5115C2.6060008@aurel32.net> <4D51190D.1000804@siemens.com> <4D511A6E.4040200@aurel32.net> In-Reply-To: <4D511A6E.4040200@aurel32.net> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Aurelien Jarno Cc: Anthony Liguori , Stefan Hajnoczi , Marcelo Tosatti , "qemu-devel@nongnu.org" , Anthony Liguori , Paul Brook , "Edgar E. Iglesias" , Paolo Bonzini , Arun Bharadwaj On 2011-02-08 11:26, Aurelien Jarno wrote: > Jan Kiszka a =E9crit : >> On 2011-02-08 11:06, Aurelien Jarno wrote: >>> Jan Kiszka a =E9crit : >>>> On 2011-02-08 10:58, Aurelien Jarno wrote: >>>>> Jan Kiszka a =E9crit : >>>>>> On 2011-02-08 10:05, Aurelien Jarno wrote: >>>>>>> Jan Kiszka a =E9crit : >>>>>>>> On 2011-02-08 09:08, Paolo Bonzini wrote: >>>>>>>>> On 02/08/2011 08:26 AM, Aurelien Jarno wrote: >>>>>>>>>> I forget to remember when we decided that AIO should be implem= ented on >>>>>>>>>> any host OS. Any pointer? >>>>>>>>> To be fair, I/O-heavy workloads are almost unusable without AIO= . For=20 >>>>>>>>> Window targets, they also crash under SMP due to the Windows AP= =20 >>>>>>>>> watchdog. But then TCG and SMP do not go very well together an= yway. >>>>>>>>> >>>>>>>>> However, I think deprecating Win32 support would be a very bad = idea. >>>>>>>> It would be too early at this point. >>>>>>>> >>>>>>>> But if Windows is once the only reason to keep tons of hardly te= sted >>>>>>>> code paths around or to invest significant additional effort to = change >>>>>>>> logic or interfaces in this area, than I would prefer that step.= I'm >>>>>>>> hacking on IOTHREAD vs. !IOTHREAD for some weeks now, and all th= ose >>>>>>>> subtle differences are really a PITA and source of various break= ages. >>>>>>>> >>>>>>>> People interested in that platform should finally realize that i= ts fate >>>>>>>> is coupled to reducing the #ifdefs as well as the design differe= nces we >>>>>>>> see right now and even more in the future. >>>>>>>> >>>>>>> The guilty here is IOTHREAD. Windows support predates IOTHREAD co= ncept, >>>>>>> it's just that people who introduce IOTHREAD didn't care about Wi= ndows >>>>>>> support at all and added these #ifdef. Disabling Windows support = because >>>>>>> of that is not fair. >>>>>> The TCG execution model won't scale long-term. It's already a main= to >>>>>> boot a quad or just dual core VM, even more when your host has at = least >>>>>> as many real cores. I'm sure we'll see multi-threaded TCG CPUs in = the >>>>>> future, and the iothread will just be one of 7, 17 or 257 threads. >>>>>> >>>>> And what's the issue with that? People don't always look for perfor= mance >>>>> when using QEMU. They even often try to emulate old machines (and n= on >>>>> x86 ones), which anyway only have one CPU. This won't change in 5 y= ears, >>>>> the only thing is that those machines will be 5 years older. >>>>> >>>>> People have to keep in mind that QEMU doesn't mean only virtualizat= ion >>>>> and doesn't mean only x86. >>>> I'm not talking about virtualization here. I'm talking about usable >>>> emulation of today's (!) embedded multi-core platforms. It matters a= lot >>>> if your test roundtrip for booting into a SMP guest and running some >>>> apps is a few 10 seconds, a few minutes or even not practically work= ing. >>>> Ever tried to boot a 16 core VM in emulation mode? I did, for fun. I >>>> just hope I'll never depend on this for work. >>> Yes, it's slow. But is it a problem? You assume that people use QEMU >>> only for emulating SMP platforms. This is a wrong assumption. Beside = the >>> x86 target, only sparc really supports SMP emulation. >> >> That's too nearsighted. SMP will be commodity on practically _any_ arc= h >> within the next years. And if QEMU doesn't keep up with it, feature an= d >> performance-wise, it will loose market share. >> >=20 > Oh commercial arguments now. I am looking for something that answer my > needs, not about market share. >=20 "Market share" simply means user base, for commercial or for hobby, academic, whatever use. QEMU has a nice position here ATM. Even commercial competitors can help continuously comparing their solutions with QEMU (I once enjoyed such a product presentation). However, time does not stand still. Jan --=20 Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux