Hyperthreading in HPUX

What is hyperthreading

Its a new feature supported in HPUX 11iv3. Its supported only on Integrity system architecture (Itanium duel core processors). Basically after enabling hyperthreading (will be called as HT in this post henceforth) on server, it allows single process to spawn threads on multiple cores at a time. This speed up the processing and in turns enhances performance.

Howto enable it

HT can be enabled at hardware level and also on OS level. While toggling this settings reboot is required for changes to take effect.

Enable/disable HT at hardware levelĀ 

There are several ways to do it depends on your server’s environment.

From HPUX OS shell by setting -HT (-m parameter) to on or off in setboot configuration. Also for vpars one can use parmodify command.

From EFI shell i.e. during boot

From vPar monitor i.e. vpmon prompt


Enable/disable HT at OS levelĀ 

This can be done by setting kernel parameter logical CPU attribute to 1 on 0 in kernel configurations.

You need to reboot the system after making these changes so that kernel will boot with HT feature.

Any thoughts?