Specifications

VMware, Inc. 335
Chapter 12 VMware ESX Server Resource Management
maximum!usage!by!a!virtual!machine.!Shares!represent!relative!importance!or!priority.!
You!set!shares!to!specify!which!virtual!machines!will!get!preferential!treatment!when!
ESX!Server!is!constrained.
For!example,!virtual!machine!A!has!a!minimum!CPU!percentage!of!20%,!and!a!
maximum!CPU!percentage!of!50%,!while!virtual!machine!
B!has!a!minimum!percentage!
of!30%!and!no!specified!maximum!percentage.!You!give!virtual!machine!A!high!CPU!
shares!and!virtual!machine!B!low!CPU!shares.!
ESX!Server!interprets!this!allocation!so!that!virtual!machine!A!will!never!have!less!than!
20%!of!a!single!physical!CPU,!and!virtual!machine
!B!will!never!have!less!than!30%!of!a!
single!physical!CPU,!in!any!situation.
However,!if!one!or!more!virtual!machines!are!idling,!ESX!Server!redistributes!this!extra!
CPU!time!proportionally,!based!on!the!virtual!machines’!CPU!shares.!Active!virtual!
machines!benefit!when!extra!resources!are!available.!In!the!example,
!virtual!machine!A!
gets!four!times!as!much!CPU!time!as!virtual!machine!B,!subject!to!the!specified!CPU!
percentages.!(By!default!the!setting!for!high!shares!is!four!times!that!for!low!shares.)
That!is,!virtual!machine!A!has!four!times!as!much!CPU!time!as!machine!B,!as!long
!as!
the!virtual!machine!A’s!CPU!percentage!is!between!20%!and!50%.!Actually,!virtual!
machine!A!might!get!only!twice!the!CPU!time!of!virtual!machine!B,!because!four!times!
the!CPU!time!exceeds!50%,!or!the!maximum!CPU!percentage!of!virtual!machine!A.
Using Hyper-Threading
You!can!enable!Hyper‐threading!to!allow!a!single!processor!to!execute!two!
independent!threads!simultaneously.!While!this!feature!does!not!provide!the!
performance!of!a!true!dual‐processor!system,!it!can!improve!utilization!of!on‐chip!
resources,!leading!to!greater!throughput!for!certain!important!workloads.!
Enabling Hyper-Threading in ESX Server
Enable!Hyper‐Threading!with!the!Enable!Hyper‐Threading!option!for!your!system!
startup!profile.!Set!this!option!with!Options‐>Startup!Profile!in!the!Management!
Interface.!See!“Startup!Profile”!on!page 188.
You!can!also!enable!Hyper‐Threading!in!the!Service!Console.!
To edit /etc/vmware/hwconfig and set the hyperthreading option
1Log!into!the!Service!Console!as!root.
2Edit!/etc/vmware/hwconfig
.