On Thu, Jun 12, 2008 at 7:29 PM, Malcolm Beattie <[EMAIL PROTECTED]> wrote:
> PerfKit percentages are calculated as "percentage of one engine". > Linux percentages calculate "percentage of CPU resource available to > the image". For your Linux guest with 2 engines, Linux tells you it's > using ~15% of its 2-engines'-worth. PerfKit spells that as ~30% of > a nominally-100%-utilised single engine. Same resource usage, > different way of displaying the measurement. Obviously Linux on z/VM has no idea how much is really available to it. It's just dividing things by the number of virtual CPUs. That does not mean Linux would have n * 100% available. > [For the purposes of this posting, I'm treating any remaining few > percent difference as a second order effect or else we'd muddy the > waters with discussing a bunch of more complex measurement issues.] You can ignore what you like, but the remainder is probably significant. With the later kernel releases that use the "virtual cpu accounting" (recognized by the reporting of steal percentage) the basis is virtual time rather than total time. So anything done by CP on behalf of this Linux virtual machine is reported by Linux as unused. Rob -- Rob van der Heij Velocity Software http://velocitysoftware.com/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
