El Fri, 30 Jan 2015 11:36:37 +0100 Frederic Konrad <fred.kon...@greensocs.com> escribió: > On 30/01/2015 11:26, Marc Marí wrote: > > El Fri, 30 Jan 2015 08:37:47 +0100 > > Jan Kiszka <jan.kis...@siemens.com> escribió: > >> On 2015-01-30 00:06, Paolo Bonzini wrote: > >>> > >>> On 29/01/2015 20:37, Marc Marí wrote: > >>>> Is this an expected behaviour? I can't see why. > >>>> > >>>> I'd like to know if there is a certain reason why it doesn't > >>>> work. Or if it should work and the problem is too much I/O > >>>> overhead. Or any other hint to understand it. > >>> It is due to latencies in the host. You need at least to use > >>> preempt-rt kernels in the host as well. > >> That alone won't help much. You also need to fine-tune the guest to > >> avoid running into QEMU locks that continuously synchronizes the > >> guest on things like VGA or disk I/O emulation. > >> > >> When using KVM, thus being able to run VCPUs widely independent of > >> each other and the device models, you need to push cyclictest on an > >> isolated second virtual CPU of the guest. Luiz and Marcelo can > >> probably confirm this based on their ongoing experiments. > >> > >> With TCG, we would first of all have to make it true SMP and > >> independent of the I/O device lock. That's what Frederic is working > >> on [1]. > >> > >> Jan > >> > >> [1] http://permalink.gmane.org/gmane.comp.emulators.qemu/314406 > >> > > Thanks for the answers. I think I'm stuck with ARM926, which I > > think is not prepared for SMP. I'll have to look if I can use > > Cortex for my experiments. > > > > I'll continue interested with the improvements for RT on TCG, but > > for the moment I'll go to work on real harware, even though is > > easier to run and debug on an emulator. > > > > Thanks > > Marc > Hi Marc, > > I think the important point here is "TCG thread independent of the > I/O device lock". > I need it for multithread TCG but that doesn't mean you need an SMP > guest platform for that. > > Fred >
I read too fast, sorry. What has to be multicore is the host, so the I/O can run independently of the TCG. But the guest can be multi- or uni-core. Marc
