On Thu, 2004-12-09 at 21:21, Mark Wong wrote: > On Mon, Dec 06, 2004 at 07:52:37PM +0000, Simon Riggs wrote: > > Varying bgwriter_maxpages upwards should take performance higher. > > > > I have 2 runs now. I for both tests, I have bgwriter_percent=100, > checkpoint_segments=8192, checkpoint_timout=600, > debug_shared_buffers=10, log_min_messages=debug1 and varied > bgwriter_maxpages. > > http://www.osdl.org/projects/dbt2dev/results/dev4-010/206/ > bgwriter_maxpages=100 (default) > throughput 3816.51 > > http://www.osdl.org/projects/dbt2dev/results/dev4-010/207/ > bgwriter_maxpages=1000 > throughput 3865.50 > > > Another 1% change in overall throughput. I did catch in the oprofile > output that StrategyDirtyBufferList moved down the list a bit when I > increased bgwriter_maxpages.
Checkpointing is occurring more frequently than it should be on these tests. With a setting of checkpoint_segments = 8192 and checkpoint_timeout = 600, it was expected to see checkpoints occurring every 10 minutes. This is not the case - checkpoints occur every 6m 15s (ish). That seems to reveal possible problems with the Checkpoint code: 1. The checkpoint seems to be limited to recycling 255 files at every checkpoint. That would correspond to a maximum checkpoint_segments value of 511, though the setting for the run was 8192. (guc.c shows the max value is INT_MAX and all other fields used to manipulate the value at C int, so I can't see why this should be...)....bug? 2. There is at least one case where a checkpoint started *immediately* after a checkpoint completed, i.e. less than 1 second between one ending and another starting. That seems very wrong....bug? http://www.osdl.org/projects/dbt2dev/results/dev4-010/207/db/log 2004-12-07 12:51:52 ...or was that a manual checkpoint? -- Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
