Re: [NOVICE] Fwd: Process scheduling in postgres

On Sat, Apr 23, 2016 at 11:21 AM, Sameer Kumar <sameer(dot)kumar(at)ashnik(dot)com>
wrote:

>
>
> On Fri, Apr 22, 2016 at 5:21 PM raghu vineel <raghuvineel(at)gmail(dot)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] SELECTlms 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.
>>
>> --
> --
> Best Regards
> Sameer Kumar | DB Solution Architect
> *ASHNIK PTE. LTD.*
>
> 101 Cecil Street, #11-11 Tong Eng Building, Singapore 069 533
>
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>

Yes, they query the same table. But all queries are *select* only. Postgres
is 8.3 and OS is *LINUX 2.6.32-431.el6.x86_64. *
Also I could see that pg_locks.granted is true for the queries I have
submitted and lock mode is
* AccessShareLock.*