Re: pgstat wait timeout (RE: contrib/cache_scan)
| От | Jeff Janes |
|---|---|
| Тема | Re: pgstat wait timeout (RE: contrib/cache_scan) |
| Дата | |
| Msg-id | CAMkU=1wS_UPTFzXJ2SCi8Z84Uu1AuO=N=MTz5j0EFe+=s7ANGg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: pgstat wait timeout (RE: contrib/cache_scan) (Tom Lane <tgl@sss.pgh.pa.us>) |
| Ответы |
Re: pgstat wait timeout (RE: contrib/cache_scan)
|
| Список | pgsql-hackers |
On Wed, Mar 12, 2014 at 7:42 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Kouhei Kaigai <kaigai@ak.jp.nec.com> writes:We've seen sporadic reports of that sort of behavior for years, but no
> 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).
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
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