Mark, all: So, this is pretty damming: Read-only test with HT ON: [pgtest@db ~]$ pgbench -c 20 -j 4 -T 600 -S bench starting vacuum...end. transaction type: SELECT only scaling factor: 30 query mode: simple number of clients: 20 number of threads: 4 duration: 600 s number of transactions actually processed: 47167533 tps = 78612.471802 (including connections establishing) tps = 78614.604352 (excluding connections establishing) Read-only test with HT Off: [pgtest@db ~]$ pgbench -c 20 -j 4 -T 600 -S bench starting vacuum...end. transaction type: SELECT only scaling factor: 30 query mode: simple number of clients: 20 number of threads: 4 duration: 600 s number of transactions actually processed: 82457739 tps = 137429.508196 (including connections establishing) tps = 137432.893796 (excluding connections establishing) 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". -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
