Re: High SYS CPU - need advise

Merlin,

this is not my report, probably from a thread that I've referenced as
having a common symptoms. Here is info about my db:

Postgresql 9.1.6.
Postgres usually has 400-500 connected clients, most of them are idle.
Database is over 1000 tables (across 5 namespaces), taking ~150Gb on disk.
We have mostly select statements (joins across few tables), using indexes
and resulting in a small number of records returned.

So mostly small lookups across few tables joining by a primary key / index.
Also, I just perform an experiment - I switched our app over to using hot
PITR instead of master and it experienced the same problem. So since PITR
db can only perform read-only queries, there is no write-locks (except
maybe when pitr is playing wal records from the master?), nevertheless SYS
CPU jumped sky.

-- Vlad

>
> Is this still true? Can we capture strace from one of the high %
> postmasters to see if there's any clues there. Maybe we've uncovered
> some type of weird spinlock contention issue. How large is your
> database (or at least the portion of it that's commonly used)? Would
> you characterize your queries as mostly small lookups, scans, or a
> mix?
>
> merlin
>