Marcelo Tosatti wrote:
On Mon, Jul 07, 2008 at 03:27:16PM -0300, Glauber Costa wrote:
I agree. A paravirt solution solves the problem.
Please, look at the patch I've attached.
It does __delay with host help. This may have the nice effect of not
busy waiting for long-enough delays, and may well.
It is _completely_ PoC, just to show the idea. It's ugly, broken,
obviously have to go through pv-ops, etc.
Also, I intend to add a lpj field in the kvm clock memory area. We
could do just this later, do both, etc.
If we agree this is a viable solution, I'll start working on a patch
This stops interrupts from being processed during the delay. And also
there are cases like this recently introduced break:
/* Allow RT tasks to run */
preempt_enable();
rep_nop();
preempt_disable();
I think it would be better to just pass the lpj value via paravirt and
let the guest busy-loop as usual.
I agree. VMI and Xen already pass a cpu_khz paravirt value. Something
similar would probably do the trick.
It may be worthwhile having udelay() or spinlocks call into KVM if
they've been spinning long enough but I think that's a separate discussion.
Regards,
Anthony Liguori
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