Specifications

VMware, Inc. 333
Chapter 12 VMware ESX Server Resource Management
you!deploy!an!additional!15!virtual!machines,!these!five!initial!virtual!machines!will!
receive!a!smaller!share!of!CPU!time!than!what!they!used!previously.
To!have!the!users!of!these!original!five!virtual!machines!become!accustomed!to!this!
higher!level!of!CPU!time,!set!a!maximum!CPU!percentage!for!these!
five!virtual!
machines!and!limit!the!amount!of!CPU!time!they!receiv e.!Then,!these!users!won’t!see!a!
difference!when!you!deploy!the!additional!virtual!machines.
Assigning Virtual Machines to Run on Specific Processors
In!multiprocessor!systems,!you!can!also!restrict!the!assignment!of!virtual!machines!to!
a!subset!of!the!available!processors!by!specifying!an!affinity!set!for!each!virtual!
machine.!The!system!assigns!each!virtual!machine!to!processors!in!the!specified!affinity!
set!to!achieve!the!CPU!allocations!specified!by!the!minimum,!maximum,
!and!shares!
settings!associated!with!each!virtual!machine.!If!the!affinity!set!for!a!uniprocessor!
virtual!machine!contains!a!single!processor,!the!virtual!machine!is!placed!there.!
The!scheduler!performs!automatic!load!balancing!of!CPU!time.!To!optimize!this!
automatic!load!balancing,!avoid!manually!specifying!affinity!for!a!virtual!machine.!
Instead,!set!a!CPU!minimum!to!guarantee!the!minimal!acceptable!performance!for!a!
virtual!machine.!See!“CPU!Resource!Management”!on!page 331.
You!can!modify!CPU!shares!and!affinity!sets!at!any!time!using!the!procfs!interface!on!
the!service!console!or!using!the!VMware!Management!Interface.!Initial!values!for!a!
virtual!
machine!can!be!specified!in!its!configuration!file.!
Using Proportional-share Scheduling by Allocating Shares
With!proportional‐share!processor!scheduling,!you!can!allocate!a!number!of!shares!to!
each!scheduled!virtual!machine.!CPU!shares!are!relative.!
For!example,!a!virtual!machine!that!is!allocated!2000!shares!is!entitled!to!consume!twice!
as!many!CPU!cycles!as!a!virtual!machine!with!1000!shares.!Similarly,!a!virtual!machine
!
that!is!allocated!200!shares!is!entitled!to!consume!twice!as!many!CPU!cycles!as!a!virtual!
machine!with!100!shares.!The!number!of!shares!may!vary,!but!the!first!virtual!machine!
has!twice!as!many!shares!as!the!second!virtual!machine.
N
OTE The!CPU!percentage(s)!you!choose!represent!an!absolute!fixed!limit!for!that!virtual!
machine.
NOTE By!specifying!a!minimum!(instead!of!specifying!affinity),!ESX!Server!has!the!maximum!
flexibility!for!automatic!optimizations.