Re: Sudden drop in DBb performance

From: Gerhard Wohlgenannt <wohlg(at)ai(dot)wu(dot)ac(dot)at>
To: Tomas Vondra <tv(at)fuzzy(dot)cz>
Cc: Andy Colson <andy(at)squeakycode(dot)net>, pgsql-performance(at)postgresql(dot)org, Heinz-Peter Lang <heinz(at)langatium(dot)net>, Gerhard Wohlgenannt <wohlg(at)ai(dot)wu-wien(dot)ac(dot)at>, "Weichselbraun, Albert" <albert(dot)weichselbraun(at)wu(dot)ac(dot)at>
Subject: Re: Sudden drop in DBb performance
Date: 2011-09-06 08:32:09
Message-ID: 4E65DA89.2030106@ai.wu.ac.at
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hi,

> What does a "normal load" mean? Does that mean a time when the queries are
> slow?

yes, we are have slow queries (according to postgresql.log) with such load
> Are you sure the machine really has 48GB of RAM? Because from the vmstat
> output it seems like there's just 32GB.
>
> procs -----------memory---------- ---swap-- -----io---- -system--
> ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy
> id wa
> 0 0 1342168 336936 107636 31353512 0 0 14 183 1911 3426
> 2 1 93 4
>
>
> 1342168 + 336936 + 107636 + 31353512 = 33140252 ~ 31GB

strange.
we paid for 48G :-) and top and free show 48G
/root# free
total used free shared buffers cached
Mem: 49564860 49310444 254416 0 30908 30329576
-/+ buffers/cache: 18949960 30614900
Swap: 20971512 1370960 19600552

> Otherwise I don't see anything wrong in the output. What is the size of
> the database (use pg_database_size to get it)? Did it grow significantly
> recently?
>

there are a number of databases in the cluster on that machine,
in the filesystem it adds up to 271G

cheers gerhard

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