On 06/21/2011 11:41 AM, Gleb Natapov wrote:
On Tue, Jun 21, 2011 at 11:09:21AM +0300, Avi Kivity wrote: > On 06/21/2011 09:02 AM, Gleb Natapov wrote: > >On Mon, Jun 20, 2011 at 07:34:57PM +0300, Avi Kivity wrote: > >> >The only two things which came to my mind are: > >> > > >> > * NMI (aka. ipmitool diag) - already available in qemu/kvm - but requires > >> > in-guest kexec/kdump > >> > * Hardware-Watchdog (also available in qemu/libvirt) > >> > >> A watchdog has the advantage that is also detects lockups. > >> > >And has disadvantage that all time base heuristics are bite us in the > >end. > > The perf-based watchdog counts clocks-not-halted, not time, so it is > safe from time issues. So it counts only instruction that guest actually executed? That's perfect then. How much overhead it has in a guest though?
Should be pretty low, especially if the guest is idle. There were some negative reports about the pmu From David Ahern, so it needs to be verified.
> We could make the hardware watchdog cheat in > the same way. > Something like steal time, but for watchdog. But this become complicated fast. Watchdog emulation will have to move into kernel for starter.
Why? You can use a performance counter from userspace. -- error compiling committee.c: too many arguments to function -- 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
