Re: Turn off Hyperthreading! WAS: 60 core performance with 9.3

On Wed, Aug 20, 2014 at 12:13:50PM -0700, Josh Berkus wrote:
> On a read-write test, it's 10% faster with HT off as well.
>
> Further, from their production machine we've seen that having HT on
> causes the machine to slow down by 5X whenever you get more than 40
> cores (as in 100% of real cores or 50% of HT cores) worth of activity.
>
> So we're definitely back to "If you're using PostgreSQL, turn off
> Hyperthreading".

Not sure how you can make such a blanket statement when so many people
have tested and shown the benefits of hyper-threading.  I am also
unclear exactly what you tested, as I didn't see it mentioned in the
email --- CPU type, CPU count, and operating system would be the minimal
information required.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + Everyone has their own god. +