Re: [libvirt-users] questions on clock catchup
On 03/13/2014 12:49 AM, Jincheng Miao wrote:
In http://libvirt.org/formatdomain.html#elementsTime , we could find
there are
three attributes of catchup tickpolicy: limit, threshold and slew.
"
The catchup element has three optional attributes, each a positive integer.
The attributes are threshold, slew, and limit.
"
The xml format likes:
<clock offset='utc'>
<timer name='rtc' tickpolicy='catchup'>
<catchup slew='123'/> or <catchup threshold='123'/> or
<catchup limit='123'/>
</timer>
</clock>
But there is no further explanation.
Does anyone know what's the meaning of these attributes ?
We ought to copy the documentation that qemu just added:
# Policy for handling lost ticks in timer devices.
#
# @discard: throw away the missed tick(s) and continue with future injection
# normally. Guest time may be delayed, unless the OS has explicit
# handling of lost ticks
#
# @delay: continue to deliver ticks at the normal rate. Guest time will be
# delayed due to the late tick
#
# @merge: merge the missed tick(s) into one tick and inject. Guest time
# may be delayed, depending on how the OS reacts to the merging
# of ticks
#
# @slew: deliver ticks at a higher rate to catch up with the missed
tick. The
# guest time should not be delayed once catchup is complete.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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