On Wed, Jun 09, 2010 at 05:16:47PM +0300, Avi Kivity wrote: > On 06/09/2010 04:23 PM, Marcelo Tosatti wrote: > > > >>Is there any chance that using a workqueue might help the problem of > >>hrtimers firing too quickly? I wanted to return HR_NORESTART from > >>pit_timer_fn always, then restart the hrtimer on delivery, but > >>because of unreliable delivery, it wasn't clear how to do that. > >> > >>Perhaps the workqueue can be used to restart the timer instead, > >>avoiding problems of impossibly small timeouts causing hrtimers to > >>run amok. > >It should be rearmed on ACK ideally. How come delivery is unreliable? > > > >BTW, a massive amount of hrtimers (_single_ non-tickless 32-vcpu guest > >with LAPIC) results in: > > > >hrtimer: interrupt took 122448 ns > > > >in the host. So don't even need impossibly small timeouts :( > > Any idea where that came from? Even looping on vcpus, that took 4 > usec per vcpu. The rearming of timers (that emulate LAPIC) cause the host hrtimer interrupt handler to re-execute its "run expired timers" loop. If timing is unfortunate, it'll have to do that several times. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
