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