Google Cloud Platform and Hyperthreading

Questions and other topics related to UEMS 18.
Post Reply
horac
Posts: 6
Joined: Thu Dec 10, 2009 8:36 pm

Google Cloud Platform and Hyperthreading

Post by horac » Thu Jan 24, 2019 7:46 pm

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...

NoNickName
Posts: 39
Joined: Thu Jan 06, 2011 9:10 pm

Re: Google Cloud Platform and Hyperthreading

Post by NoNickName » Fri Jan 25, 2019 2:12 pm

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.

j0nes2k
Posts: 56
Joined: Wed Feb 03, 2010 5:06 pm

Re: Google Cloud Platform and Hyperthreading

Post by j0nes2k » Wed May 22, 2019 3:34 pm

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

norulz
Posts: 95
Joined: Thu Mar 12, 2015 1:43 pm

Re: Google Cloud Platform and Hyperthreading

Post by norulz » Sat Jul 06, 2019 9:22 am

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

meteoadriatic
Posts: 1601
Joined: Wed Aug 19, 2009 10:05 am

Re: Google Cloud Platform and Hyperthreading

Post by meteoadriatic » Sat Jul 06, 2019 12:59 pm

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.

Post Reply