Re: Processor speed relative to postgres transactions per second
От | Greg Smith |
---|---|
Тема | Re: Processor speed relative to postgres transactions per second |
Дата | |
Msg-id | 4BB0EF79.1030604@2ndquadrant.com обсуждение исходный текст |
Ответ на | Processor speed relative to postgres transactions per second (Chris Barnes <compuguruchrisbarnes@hotmail.com>) |
Список | pgsql-general |
Recently I ran a set of tests on two systems: a 4-core server with 5 disks (OS + WAL + 3 for DB) on a battery backed disk controller, and a newer Hyper-threaded design with 4 physical cores turning into 8 virtual ones--but only a single disk and no RAID controller, so I had to turn off its write cache to get reliable database operation. (See http://www.postgresql.org/docs/current/interactive/wal-reliability.html ) When running pgbench with its simple built-in SELECT-only test, on a tiny data set that fits in RAM, I went from a peak of 28336 TPS on the 4-core system to a peak of 58164 TPS on the 8-core one. On the default write-heavy test, the 4-core server peaked at 4047 TPS. The 8-core one peaked at 94 TPS because that's as fast as its single disk could commit data. The moral is that a faster processor or more cores only buys you additional speed if enough of your data fits in RAM that the processor speed is the bottleneck. If you're waiting on disks, a faster processor will just spin without any work to do. You can't answer "will I get more transactions per second?" without specifying what your transaction is, and knowing what the current limiter is. -- Greg Smith 2ndQuadrant US Baltimore, MD PostgreSQL Training, Services and Support greg@2ndQuadrant.com www.2ndQuadrant.us
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