On Sun, Apr 14, 2013 at 7:34 PM, Jeff Janes <jeff.ja...@gmail.com> wrote:
> On Saturday, April 13, 2013, Rodrigo Barboza wrote: > >> >> >> >> On Sat, Apr 13, 2013 at 4:51 PM, Jeff Janes <jeff.ja...@gmail.com> wrote: >> >>> On Sat, Apr 13, 2013 at 10:29 AM, Rodrigo Barboza < >>> rodrigombu...@gmail.com> wrote: >>> >>>> >>>> >>>> I was receiving warning messages of pgstat timeout. >>>> I started looking for the solution for this problem and this doubt came >>>> out. >>>> But it doesn't seem to be the problem. >>>> >>> >>> Usually that just means that you are dirtying pages faster than your >>> hard drives can write them out, leading to IO contention. Sometimes you >>> can do something about this by changing the work-load to dirty pages in >>> more compact regions, or by changing the configuration. Often the only >>> effective thing you can do is buy more hard-drives. >>> >> > I meant congestion, not contention. > > >> >>> >> Would it help if I changed the checkpoint_completion_target to something >> close to 0.7 (mine is the default 0.5) >> > > Probably not. The practical difference between 0.5 and 0.7 is so small, > that even if it did make a difference at one place and time, it would stop > making a difference again in the future for no apparent reason. > > >> or raise the checkpoint_segments (it is 32 now)? >> > > Maybe. If you are dirtying the same set of pages over and over again, and > that set of pages fits in shared_buffers, then lengthening the time between > checkpoints could have a good effect. Otherwise, it probably would not. > > Your best bet may be just to try it and see. But first, have you tried to > tune shared_buffers? > > What are you doing? Bulk loading? Frantically updating a small number of > rows? > > Do you have pg_xlog on a separate IO controller from the rest of the data? > Do you have battery-backed/nonvolatile write cache? > > Cheers, > > Jeff > My shared_buffer is tuned for 25% of memory. My pg_xlog is in the same device. It is not bulk loading, The battery I have to check, because the machine is not with me.
