On Wed, Mar 12, 2014 at 7:42 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Kouhei Kaigai <kai...@ak.jp.nec.com> writes: > > WARNING: pgstat wait timeout > > WARNING: pgstat wait timeout > > WARNING: pgstat wait timeout > > WARNING: pgstat wait timeout > > > Once I got above messages, write performance is dramatically > > degraded, even though I didn't take detailed investigation. > > > I could reproduce it on the latest master branch without my > > enhancement, so I guess it is not a problem something special > > to me. > > One other strangeness is, right now, this problem is only > > happen on my virtual machine environment - VMware ESXi 5.5.0. > > I couldn't reproduce the problem on my physical environment > > (Fedora20, core i5-4570S). > > We've seen sporadic reports of that sort of behavior for years, but no > developer has ever been able to reproduce it reliably. Now that you've > got a reproducible case, do you want to poke into it and see what's going > on? > I didn't know we were trying to reproduce it, nor that it was a mystery. Do anything that causes serious IO constipation, and you will probably see that message. For example, turn off synchronous_commit and run the default pgbench transaction at a large scale but that still comfortably fits in RAM, and wait for a checkpoint sync phase to kick in. The pgstat wait timeout is a symptom, not the cause. Cheers, Jeff
