| From: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
|---|---|
| To: | Thomas Pöhler <tp(at)turtle-entertainment(dot)de> |
| Cc: | pgsql-performance(at)postgresql(dot)org, Felix Feinhals <ff(at)turtle-entertainment(dot)de>, Verteiler_A-Team <a-team(at)turtle-entertainment(dot)de>, Björn Metzdorf <bm(at)turtle-entertainment(dot)de> |
| Subject: | Re: high user cpu, massive SELECTs, no io waiting problem |
| Date: | 2011-02-15 18:01:53 |
| Message-ID: | AANLkTikLYb1+4-ZUYvDV3uzQ3TB1qFkGVv1FH=eSiRxZ@mail.gmail.com |
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| Lists: | pgsql-performance |
On Tue, Feb 15, 2011 at 10:19 AM, Thomas Pöhler
<tp(at)turtle-entertainment(dot)de> wrote:
> Since a few weeks we have really strange peaks on this system. User CPU is
> increasing up to 100% and we have lots of SELECTs running.
Are you using pooling of some kind, or do you have LOTS of connections?
> There is no iowait at this time, only high user cpu and we don’t know where
> this is coming from. It seems like this is only happening under certain
> circumstances.
run htop and look for red. if youi've got lots of red bar on each CPU
but no io wait then it's waiting for memory access. Most of these
multi-core machines will be memory read / write speed bound. Pooling
will help relieve some of that memory bandwidth load, but might not be
enough to eliminate it.
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