On Thu, Aug 21, 2014 at 02:02:26PM -0700, Josh Berkus wrote: > On 08/20/2014 07:40 PM, Bruce Momjian wrote: > > 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. > > Actually, I don't know that anyone has posted the benefits of HT. Link? > I want to compare results so that we can figure out what's different > between my case and theirs. Also, it makes a big difference if there is > an advantage to turning HT on for some workloads. I had Greg Smith test my system when it was installed, tested it, and recommended hyper-threading. The system is Debian Squeeze (2.6.32-5-amd64), CPUs are dual Xeon E5620, 8 cores, 16 virtual cores. -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
