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How to enable hyperthreading on Itanium

Q:I would like to turn on hyperthreading for my system. How can I do this and can it be done on a running system?

A:Hyperthreading is only available on certain models of Itanium systems. There are two steps:

 

Step 1:
Use
setboot –m on to enable hyperthreading.
Only certain systems support hyperthreading.
Check with
setboot–v
This may require a reboot.


Step 2:
C
hange the kernel parameter lcpu_attr from 0 to 1
View the current setting:
# kctune –q lcpu_attr
Tunable Value Expression Changes
lcpu_attr 0 0 Imm (auto disabled)

# kctune lcpu_attr=1

* The automatic ‘backup’ configuration has been updated.
* The requested changes have been applied to the currently
  running configuration
Tunable              Value  Expression  Changes
lcpu_attr  (before)      0  0           Imm (auto disabled)

           (now)         1  1

The fastest way to see the effect is to run top and you’ll see all the processors listed.

Whether this will have an effect on your system performance is a somewhat complicated answer. The output from uptime (and top) will show the load average which will be the average of all the CPUs taken as a whole. So for a 2 CPU system, one processor idle and the other maxed out to 100% is a load average of 0.50. Generally speaking, if the load average is more than 1.00, hyperthreading may improve performance.

– See more at: https://serviceitdirect.com/blog/how-enable-hyperthreading-itanium#sthash.8nZ5oshp.dpuf

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Categories: HP-UX