All tests were done with a custom load testing script that used some particularly problematic query that I dont have here. The number of requests of almost all test was 300, that was a meaningful number for our tests. ===================================================================================================== FreeBSD 7.2 + MySQL 5.1 - Cores Test Results: ===================================================================================================== 2 cores - 300 requests Start 11:30:52 Finish 11:31:35 Elapsed 00:00:43 4 cores - 300 requests Start 11:46:46 Finish 11:47:59 Elapsed 00:01:13 10/300 timeouts 8 cores - 300 requests Start 12:46:26 Finish 12:48:33 Elapsed 00:02:07 16 cores - 300 requests Start 15:27:09 Finish 15:29:23 Elapsed 00:02:14 lots of timeouts ===================================================================================================== FreeBSD 8 + MySQL 5.1 - Cores Test Results: ===================================================================================================== 2 cores (1 cpu) - 300 requests Start 18:45:49 Finish 18:46:40 Elapsed 00:00:51 Load Max 2.50 some timeouts 2 cores (separate cpu) - 300 requests Start 18:14:25 Finish 18:15:39 Elapsed 00:01:14 Load Max 2.50 umtxn and timeouts 4 cores (separate cpu)- 300 requests Start 18:08:05 Finish 18:09:17 Elapsed 00:01:12 Load Max 11.51 umtxn and timeouts 4 cores (1 cpu)- 300 requests Start 18:21:59 Finish 18:22:42 Elapsed 00:00:43 Load Max 4.50 NO TIMEOUTS 5 cores - 300 requests Start 18:03:04 Finish 18:04:32 Elapsed 00:01:28 umtxn and timeouts 8 cores (2 cpu)- 300 requests Start 18:33:49 Finish 18:35:12 Elapsed 00:01:23 Load Max 12.50 umtxn and timeouts 9 cores - 300 requests Start 17:42:41 Finish 17:44:40 Elapsed 00:01:59 umtxn and timeouts 16 cores - 300 requests Start Finish Elapsed ================================================================= FreeBSD 8 + MySQL 5.5.1.2 - Core test results ================================================================= CONF: 16 cores / 4 cpus --COLD-- --COLD-- --WARM-- --WARM-- --WARM-- INNODB-C INNODB-W Start 12:57:28 15:15:16 15:17:33 15:51:38 15:56:17 15:01:24 15:02:37 Finish 12:59:49 15:16:59 TIMEOUT 15:54:07 15:58:40 15:01:57 15:03:01 Elapsed 00:02:21 00:01:43 00:02:29 00:02:23 00:00:33 00:00:24 Load 208 238 254 5 5 Remarks: lots of umtxn and timeouts timeouts no prob no prob CONF: 4 cores / 1 cpu --COLD-- --WARM-- --WARM-- QCACHE=0 KCACHE=0 -INNODB- Start 14:07:20 14:09:54 14:12:31 14:15:17 14:20:09 14:34:57 Finish 14:08:01 14:10:32 14:13:17 14:16:04 14:20:47 14:35:20 Elapsed 00:00:41 00:00:38 00:00:46 00:00:47 00:00:38 00:00:23 Load 8 30 33 35 8 5 Remarks: no problems CONF: 5(2+3) cores / 2 cpus --COLD-- --WARM-- Start 16:11:01 16:13:39 Finish 16:12:13 16:14:41 Elapsed 00:01:12 00:01:02 Load 5 8 Remarks: lots of umtxn and timeouts timeouts no prob no prob ===================================================================================================== Linux CentOS 5.4 + MySQL 5.1 - Cores Test Results: ===================================================================================================== DEFAULT SETTINGS: 16 cores - 300 requests --COLD-- --WARM-- --WARM-- --WARM-- --WARM-- Start 14:39:37 14:46:43 14:51:39 14:53:54 14:55:29 Finish 14:40:16 14:47:27 14:52:11 14:54:33 14:56:00 Elapsed 00:00:39 00:00:44 00:00:33 00:00:39 00:00:31 Load 4.78 23.68 31.60 29.55 Remarks Smooth Smooth Smooth BIG BUFFERS SETTINGS: 16 cores - 300 requests --COLD-- --WARM-- --WARM-- Start 15:32:21 15:34:24 15:35:51 Finish 15:32:53 15:34:57 15:36:19 Elapsed 00:00:32 00:00:33 00:00:28 Load 21 23 19 Remarks Smooth Smooth Smooth BIG BUFFERS SETTINGS: 16 cores - 400 requests --WARM-- --WARM-- --WARM-- Start 15:40:01 15:41:20 15:42:56 Finish 15:40:36 15:41:55 15:43:35 Elapsed 00:00:35 00:00:35 00:00:39 Load 19 20 BIG BUFFERS SETTINGS: 16 cores - 500 requests --WARM-- --WARM-- Start 15:44:27 15:45:57 Finish 15:45:26 15:46:50 Elapsed 00:00:59 00:00:53 Load 22 50 BIG BUFFERS SETTINGS: 16 cores - 1000 requests --WARM-- Start 15:47:30 Finish 15:52:14 Elapsed 00:04:44 Load 56 Remarks bottleneck: web server -- Claudio