We see high steal time when our virtual machines have multiple virtual CPU's (but equal to or less than the number of real engines on the LPAR) and the number of virtual CPU's defined in total are more than the number of real engines. We are also over committed for memory. In the ESALPS ESALNXV report, some of the virtual machines consistently use less than the number of virtual CPU's defined. Could this also be a case of wait-on-myself?
Betsie -----Original Message----- From: Linux on 390 Port [mailto:[email protected]] On Behalf Of Rob van der Heij Sent: Wednesday, December 31, 2008 6:43 AM To: [email protected] Subject: Re: VMSTAT steals On Wed, Dec 31, 2008 at 11:38 AM, Harder, Pieter <[email protected]> wrote: > Just for clarification, you are talking 'other virtual machines', I am talking 'other VMBKs'. There is a difference there in my opinion. Another VMBK may very well be your own sibling in a virtual N-way configuration. The worst case for this would be in the (of course not recommended) situation when there are more virtual cpu's defined to the vm than there are real cpu's available. Then steal time basically becomes wait-om-myself time, true? You're correct. A simple way to show CPU contention is to define a virtual 2-way when z/VM has only one logical CPU. With two threads looping, vmstat shows me 49% user and 51% steal. Since CP will try to give both virtual CPUs an equal share of the real resources, Linux will see two CPUs running at half speed effectively. Rob -- Rob van der Heij Velocity Software http://www.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 ---------------------------------------------------------------------- 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
