Re: high user cpu, massive SELECTs, no io waiting problem

On Tue, Feb 15, 2011 at 10:19 AM, Thomas Pöhler
<tp@turtle-entertainment.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.