Re: Fwd: Process scheduling in postgres

On 4/22/2016 1:30 AM, raghu vineel wrote:
>
> I have a 4 core CPU for postgres and I have submitted 6 queries
> parallely in 6 different sessions. But I am seeing only 1 query per
> CPU and the remainig queries are queued. I am not sure why is it
> happening. Do you have any special scheduler for postgres? I can see
> that CPU has been shared with other non postgres processes but
> postgres processes are not sharing any CPU within a core. The
> following is the process states.
> *
> lms 2868 2209 98 07:20 ? 00:02:30 postgres: lms
> controller [local] SELECT
> lms 2869 2209 98 07:20 ? 00:02:30 postgres: lms
> controller [local] SELECT*
> lms 2870 2209 0 07:20 ? 00:00:00 postgres: lms
> controller [local] SELECT
> lms 2871 2209 0 07:20 ? 00:00:00 postgres: lms
> controller [local] SELECT
> lms 2872 2209 0 07:20 ? 00:00:00 postgres: lms
> controller [local] SELECT
> *lms 2873 2209 98 07:20 ? 00:02:30 postgres: lms
> controller [local] SELECT*
>
> If you see above, three Select queries have been queued. They are
> acquiring CPU only when there is a core without any postgres query
> running on it.
>
> I know the postgres limitation of one query using only one core. But
> is there any limitation of one CPU running only one query at a time?

no such limitation. any chance there's locking involved here? take a
look at pg_locks and pg_stat_activity the next time you run such a test.

--
john r pierce, recycling bits in santa cruz