Disable multithreading option on T5240

UNIX Solaris
1

Hi Gurus

Can any one tell me the process of disabling the multithreading option on T5240 server and my OS is on LDOM, having one physical processor with 8 core & 8 thread per core

Regards

2

Multithreading isn't that much an option but more a feature of the T series servers. If you really want to disable chip-multithreading, your can limit the available virtual CPU to one for the target ldom Operating System with this command:

# ldm set-vcpu 1 ldom

This is also doable at the process level with process binding or processor sets.

3

Hi all

I came to know that if we use psradm command to disable all threads, except 0, 3 ,7,11 . Through this process we can disable the threads. But can any one tell me why cann't we disable 0,3,7,11 threads. I haven't done above process as my server is production. If any one have test T-series server having oracle database or application which is single thread base. As I believe above process will increase some or bit increase performance gain for singe thread application or database. But this process will not give us significant performance gain as per that person due to same clock speed of CPU. Looking for answer of my question.

Regards

4

What you call threads are known under Solaris as virtual CPUs (or strands).

Disabling virtual CPUs 0,3,7,11 seems to me an odd advice. Assuming the goal is to leave a single strand active per core, I would expect it to be something like 0,8,16,24 or if you have a 4 core CPU, or 0,9,16,24,32,40 with a 6 core model and 0,8,16,24,32,40,48,56 with the 8 core model.
Anyway, it is unclear what you are trying to achieve. In your first question, you stated you were using an ldom but you don't tell how many virtual CPUs are available to the ldom OS.

Are there multiple processes competing for the CPUs on your server ? What is its reported load during peak periods ?

Disabling CPU strands isn't really something you can expect to improve performance but more to reduce it.

If you happen to run the latest Solaris 10 (8/11) or Solaris 11, you might instead have a look at the Critical Threads Optimization, although I'm not sure about its impact, if any, in your case.

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