Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1XKZdj-000277-6J for pgsql-performance@arkaria.postgresql.org; Thu, 21 Aug 2014 21:11:23 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.80) (envelope-from ) id 1XKZdi-0000O4-Eq for pgsql-performance@arkaria.postgresql.org; Thu, 21 Aug 2014 21:11:22 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1XKZdh-0000Ny-N6 for pgsql-performance@postgresql.org; Thu, 21 Aug 2014 21:11:21 +0000 Received: from momjian.us ([72.94.173.45]) by magus.postgresql.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1XKZdd-0007kn-TA for pgsql-performance@postgresql.org; Thu, 21 Aug 2014 21:11:20 +0000 Received: from bruce by momjian.us with local (Exim 4.72) (envelope-from ) id 1XKZdZ-00088X-US; Thu, 21 Aug 2014 17:11:13 -0400 Date: Thu, 21 Aug 2014 17:11:13 -0400 From: Bruce Momjian To: Josh Berkus Cc: pgsql-performance@postgresql.org, Mark Kirkwood , "Graeme B. Bell" , Greg Smith Subject: Re: Turn off Hyperthreading! WAS: 60 core performance with 9.3 Message-ID: <20140821211113.GD26706@momjian.us> References: <53ACB190.2030206@catalyst.net.nz> <53ECFD75.3060408@agliodbs.com> <53ED371D.109@catalyst.net.nz> <53F4F36E.6050003@agliodbs.com> <20140821024036.GB26706@momjian.us> <53F65E62.3020909@agliodbs.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53F65E62.3020909@agliodbs.com> User-Agent: Mutt/1.5.20 (2009-06-14) X-Pg-Spam-Score: -2.6 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org 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 http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance