Re: pgstat wait timeout

On 15 Prosinec 2011, 18:19, Magnus Hagander wrote:
> On Thu, Dec 15, 2011 at 18:13, Tomas Vondra <tv(at)fuzzy(dot)cz> wrote:
>> On 15 Prosinec 2011, 17:55, pratikchirania wrote:
>>> Hi,
>>>
>>> I am having a scenario where I get consistent warnings in the pglog
>>> folder:
>>>
>>> 2011-12-11 00:00:03 JST WARNING:  pgstat wait timeout
>>> 2011-12-11 00:00:14 JST WARNING:  pgstat wait timeout
>>> 2011-12-11 00:00:24 JST WARNING:  pgstat wait timeout
>>> 2011-12-11 00:00:31 JST WARNING:  pgstat wait timeout
>>> 2011-12-11 00:00:44 JST WARNING:  pgstat wait timeout
>>> 2011-12-11 00:00:52 JST WARNING:  pgstat wait timeout
>>> 2011-12-11 00:01:03 JST WARNING:  pgstat wait timeout
>>> 2011-12-11 00:01:11 JST WARNING:  pgstat wait timeout
>>>
>>> This is impacting database performance.
>>
>> It's rather a sign that the I/O is overloaded, although in some cases it
>> may actually be the cause.
>>
>>> The issue persists even when I use the database minimally.
>>
>> Yes, because the file is written periodically - twice a second IIRC. If
>> the file is large, this may be an issue. What is the pgstat.stat size
>> (should be in data/global).
>
> That was only true prior to 8.4. As of 8.4 it's only written when
> necessary, which is usually a lot less than twice / second.

Thanks for the correction. Nevertheless, it would be useful to know what
is the size of the file and what is the I/O usage.

Pratik, can you post the size of the pgstat.stat file and post a few lines
of "iostat -x 1" collected when the "pgstat wait timeout" happens?

Tomas