On 28.4.2014 16:07, Tom Lane wrote: > Elanchezhiyan Elango <elanelango@xxxxxxxxx> writes: >>> The problem is that while this makes the checkpoints less >>> frequent, it accumulates more changes that need to be written to >>> disk during the checkpoint. Which means the impact more severe. > >> True. But the checkpoints finish in approximately 5-10 minutes >> every time (even with checkpoint_completion_target of 0.9). > > There's something wrong with that. I wonder whether you need to > kick checkpoint_segments up some more to keep the checkpoint from > being run too fast. > > Even so, though, a checkpoint spread over 5-10 minutes ought to > provide the kernel with enough breathing room to flush things. It > sounds like the kernel is just sitting on the dirty buffers until it > gets hit with fsyncs, and then it's dumping them as fast as it can. > So you need some more work on tuning the kernel parameters. There's certainly something fishy, because although this is the supposed configuration: checkpoint_segments = 250 checkpoint_timeout = 1h checkpoint_completion_target = 0.9 the checkpoint logs typically finish in much shorter periods of time. Like this, for example: > > regards, tom lane > > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
