could that because of my system is really busy? 1, postgresql always have 400+ connections(dozens of python process using client pool) 2, the query peak is 50+/s 3, I do have some bad performance sql executing periodically, need 100+ second to complete. could those bad performance sql influence others? because when I execute those simple sql directly, they was fast. but the slow query log shows it took too much time.
On Wed, Jul 11, 2012 at 4:23 PM, Albe Laurenz <laurenz.a...@wien.gv.at>wrote: > Yan Chunlu wrote: > > I have logged one day data and found the checkpoint is rather > frequently(detail: > > https://gist.github.com/3088338). Not sure if it is normal, but the > average time of checkpoint is > > about 100sec~200sec, it seems related with my settings: > > > > 574 checkpoint_segments = 64 > > 575 wal_keep_segments = 5000 > > > > I set checkpoint_segments as a very large value which is because > otherwise the slave server always can > > not follow the master, should I lower that value? > > You mean, you set wal_keep_segments high for the standby, right? > > wal_keep_segments has no impact on checkpoint frequency and intensity. > > You are right that your checkpoint frequency is high. What is your value > of checkpoint_timeout? > > You can increase the value of checkpoint_segments to decrease the > checkpoint frequence, but recovery will take longer then. > > > or the slow query is about something else? thanks! > > I guess the question is how saturated the I/O system is during > checkpoints. But even if it is very busy, I find it hard to believe > that such a trivial statement can take extremely long. > > Yours, > Laurenz Albe >
