Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default

[Edgar E. Iglesias]

On Mon, Feb 07, 2011 at 02:03:50PM -0200, Marcelo Tosatti wrote:
> On Mon, Feb 07, 2011 at 08:12:55AM -0200, Marcelo Tosatti wrote:
> > > > One more thing I didn't mention on the email-thread or on IRC is
> > > > that last time I checked, qemu with io-thread was performing
> > > > significantly slower than non io-thread builds. That was with
> > > > TCG emulation (not kvm). Somewhere between 5 - 10% slower, IIRC.
> > 
> > Can you recall what was the test ?
> > 
> > > > Also, although -icount & iothread no longer deadlocks, icount
> > > > still sometimes performs incredibly slow with the io-thread (compared
> > > > to non-io-thread qemu). In particular when not using -icount auto but
> > > > a fixed ticks per insn values. Sometimes it's so slow I thought it
> > > > actually deadlocked, but no it was crawling :) I haven't had time
> > > > to look at it any closer but I hope to do soon.
> 
> Edgar, please give the attached patch a try with fixed icount value. The
> calculation for next event makes no sense for iothread timeout, only for
> vcpu context.


Thanks Marcelo, this patch fixes the problems I was seeing here.

Cheers


> diff --git a/cpus.c b/cpus.c
> index 9c50a34..2280db1 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -748,7 +748,7 @@ static void qemu_tcg_wait_io_event(void)
>      CPUState *env;
>  
>      while (!any_cpu_has_work())
> -        qemu_cond_timedwait(tcg_halt_cond, &qemu_global_mutex, 1000);
> +        qemu_cond_timedwait(tcg_halt_cond, &qemu_global_mutex, 
> qemu_calculate_timeout());
>  
>      qemu_mutex_unlock(&qemu_global_mutex);
>  
> diff --git a/vl.c b/vl.c
> index 837be97..dbd81a1 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1323,7 +1323,7 @@ void main_loop_wait(int nonblocking)
>      if (nonblocking)
>          timeout = 0;
>      else {
> -        timeout = qemu_calculate_timeout();
> +        timeout = 1000;
>          qemu_bh_update_timeout(&timeout);
>      }
>