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. -- Aurelien Jarno GPG: 1024D/F1BCDB73 aurel...@aurel32.net http://www.aurel32.net
