Re: [NOVICE] Fwd: Process scheduling in postgres

On Fri, Apr 22, 2016 at 5:21 PM raghu vineel <raghuvineel@gmail.com> wrote:

Hi,

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?

Are all the queries related to the same table(s)?

Which version of PostgreSQL? What's the version of OS?

Check out the locks which are not granted yet - pg_locks.granted

 

Your help is appreciated.

Thanks and regards,

Vineel.

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