HP-UX Virtual Partitions Administrator's Guide (includes A.05.02)

CPU, Memory, and I/O Resources (A.05.xx)
CPU: Hyperthreading ON/OFF (HT ON/OFF)
Chapter 6
228
CPU: Hyperthreading ON/OFF (HT ON/OFF)
Hyperthreading is a new feature supported in HP-UX 11i v3 (11.31) environments on servers with the dual
core Intel Itanium 2 processors. It provides for executing multiple threads on a single core. This allows
multiple hardware threads to share under-utilized resources, increasing overall throughput and performance.
Throughput increases are typically achieved by making use of the idle cycles and idle functional units that
occur due to memory stalls. For more information on hyperthreading and performance, see the white paper
Dynamic Logical Processors for Hyper-Threading on HP-UX 11i v3 available at http://docs.hp.com.
Hyperthreading is supported within vPars A.05.xx environments. However, note the following details.
• HT ON/OFF can be set using any of the following commands.
— The vPar Monitor’s threads command.
The syntax is:
threads [on|off]
For example:
MON> threads
HyperThreading is currently OFF
HyperThreading will be OFF after the next nPar reboot
MON> threads on
HyperThreading is now set to be ON after the next reboot
MON> threads
HyperThreading is currently OFF
HyperThreading will be ON after the next nPar reboot
MON> threads off
HyperThreading is now set to be OFF after the next reboot
— The EFI shell’s cpuconfig command.
The syntax is:
cpuconfig threads [on|off]
For a primer on cpuconfig, see “Setting Hyperthreading (HT ON/OFF) and cpuconfig Primer” on
page 301.
— The HP-UX shell’s parmodify command.
The syntax is:
parmodify -T y|n
— The HP-UX shell’s setboot command.
The syntax is:
setboot -m on|off
For more information on using or setting HT ON/OFF, please see the nPartition Administrator's Guide.
• Although hyperthreading is supported within vPars, CPU assignments to virtual partitions remain on a
per-core basis and not on a logical CPU (LCPU) basis.