On 2011-02-08 11:26, Aurelien Jarno wrote: > Jan Kiszka a écrit : >> On 2011-02-08 11:06, Aurelien Jarno wrote: >>> Jan Kiszka a écrit : >>>> On 2011-02-08 10:58, Aurelien Jarno wrote: >>>>> Jan Kiszka a écrit : >>>>>> On 2011-02-08 10:05, Aurelien Jarno wrote: >>>>>>> Jan Kiszka a écrit : >>>>>>>> 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 implemented >>>>>>>>>> on >>>>>>>>>> any host OS. Any pointer? >>>>>>>>> To be fair, I/O-heavy workloads are almost unusable without AIO. For >>>>>>>>> Window targets, they also crash under SMP due to the Windows AP >>>>>>>>> watchdog. But then TCG and SMP do not go very well together anyway. >>>>>>>>> >>>>>>>>> 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 tested >>>>>>>> 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 those >>>>>>>> subtle differences are really a PITA and source of various breakages. >>>>>>>> >>>>>>>> People interested in that platform should finally realize that its fate >>>>>>>> is coupled to reducing the #ifdefs as well as the design differences we >>>>>>>> see right now and even more in the future. >>>>>>>> >>>>>>> The guilty here is IOTHREAD. Windows support predates IOTHREAD concept, >>>>>>> it's just that people who introduce IOTHREAD didn't care about Windows >>>>>>> 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 performance >>>>> when using QEMU. They even often try to emulate old machines (and non >>>>> x86 ones), which anyway only have one CPU. This won't change in 5 years, >>>>> the only thing is that those machines will be 5 years older. >>>>> >>>>> People have to keep in mind that QEMU doesn't mean only virtualization >>>>> 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 working. >>>> 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_ arch >> within the next years. And if QEMU doesn't keep up with it, feature and >> performance-wise, it will loose market share. >> > > Oh commercial arguments now. I am looking for something that answer my > needs, not about market share. >
"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 -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
