Re: time command in vm

[Christian Borntraeger <borntraeger@de.ibm.com>]

Am Dienstag, 2. September 2008 schrieb David S. Ahern:
> 
> Terry wrote:
> > Hi All,
> > 
> > When we use time command in vm, we can get 'elapsed time', 'user time'
> > and 'system time'.  How to explain these three times in detail?  For
> > example, when we have a shadow page fault, we exit from guest to host
> > for handling the fault.  So, this handling time should be considered in??
> > 
> 
> I believe the time spent within kvm handling faults and such for the
> guest shows up as system time to the guest.
> 
> david

It depends on the time accounting.

Systems with CONFIG_VIRT_CPU_ACCOUNTING (s390 and ppc64) will account host 
page fault handling as steal time in the guest. guest user and guest system 
time remain unchanged. (Host system time will increase of course)

On other systems (e.g. x86), I think the host page fault time will be 
accounted to either guest system or guest user, depending on where the next 
tick triggers accouting. 

elapsed time will increase on both kind of system.

Christian