On Thu, Mar 22, 2012 at 6:07 AM, Robert Haas <robertmh...@gmail.com> wrote: > On Wed, Mar 21, 2012 at 3:38 PM, Robert Haas <robertmh...@gmail.com> wrote: >> It looks like I neglected to record that information for the last set >> of runs. But I can try another set of runs and gather that >> information. > > OK. On further review, my previous test script contained several > bugs. So you should probably ignore the previous set of results. I > did a new set of runs, and this time bumped up checkpoint_segments a > bit more, in the hopes of giving the cache a bit more time to fill up > with dirty data between checkpoints. Here's the full settings I used: > > shared_buffers = 8GB > maintenance_work_mem = 1GB > synchronous_commit = off > checkpoint_timeout = 15min > checkpoint_completion_target = 0.9 > wal_writer_delay = 20ms > log_line_prefix = '%t [%p] ' > log_checkpoints='on' > checkpoint_segments='1000' > checkpoint_sync_pause='3' # for the checkpoint-sync-pause-v1 branch only > > With that change, each of the 6 tests (3 per branch) involved exactly > 2 checkpoints, all triggered by time rather than by xlog.
Are you sure this is the case? If the server was restarted right before the pgbench -T 1800, then there should 15 minutes of no checkpoint, followed by about 15*0.9 minutes + some sync time of one checkpoint, and maybe just a bit of the starting of another checkpoint. If the server was not bounced between pgbench -i and pgbench -T 1800, then the first checkpoint would start at some unpredictable time into the benchmark run. Cheers, Jeff -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers