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Google Cloud Platform and Hyperthreading

Posted: Thu Jan 24, 2019 7:46 pm
by horac
Hallo,

We are using Google Cloud Platform for running UEMS. From v18.x UEMS are running only on half of CPU amount. It looks like problem with Hyperthreading ON...

Does anyone have any idea how to solve this problem?

Thank You

Horac

P.S. before v18.x I wrote on EMS.profile twice CPU quantity, and I used all the CPUs...

Re: Google Cloud Platform and Hyperthreading

Posted: Fri Jan 25, 2019 2:12 pm
by NoNickName
It seems that the new versions does not rely on logical processors, but physical processors, therefore a 4-core 8-thread CPU only runs of 4 threads.
In my virtual machine host I set to give 8 cpus to the guest machine and UEMS runs on 4.

Re: Google Cloud Platform and Hyperthreading

Posted: Wed May 22, 2019 3:34 pm
by j0nes2k
Hello,

horac, did you find a solution for your problem? I am running into the same issue on Amazon Webservices. No matter what I set in run_cpus.conf or EMS.cshrc, UEMS only runs of half the cores.

Best regards,

Jonas

Re: Google Cloud Platform and Hyperthreading

Posted: Sat Jul 06, 2019 9:22 am
by norulz
It is possible to set the number of cpus and to stop the hyperthreading of an E2C instance, at least on Ubuntu distros

This is what I used:

edit /etc/default/grub

if you want 16 cores for c3.8xlarge for e.g you'd edit:

Code: Select all

GRUB_CMDLINE_LINUX_DEFAULT="console=tty1 console=ttyS0 maxcpus=16"
GRUB_CMDLINE_LINUX="maxcpus=16"
then run

Code: Select all

sudo update-grub
then reboot.

There is a long discussion of options to stop hyperthreading at https://forums.aws.amazon.com/message.j ... eID=538321

Re: Google Cloud Platform and Hyperthreading

Posted: Sat Jul 06, 2019 12:59 pm
by meteoadriatic
A quick note. The best way to chose if HT would be beneficial or detrimental is to test out with/without running your operational domain and see which setup is faster. But generally, there are some guidelines that are not mentioned in UEMS as far as I know. There is a range of optimal number of threads that can be estimated according to your total domain(s) size using this:
http://www2.mmm.ucar.edu/wrf/users/FAQ_ ... ntime.html
(Q1/A1)

So depending on how large your domains are, you might actually benefit from HT in some cases.