Re: Hmmm... why does CPU-intensive pl/pgsql code parallelise so badly when queries parallelise fine? Anyone else seen this?

On Wed, Jul 8, 2015 at 10:52 AM, Joshua D. Drake <jd(at)commandprompt(dot)com>
wrote:

>
> On 07/08/2015 10:48 AM, Craig James wrote:
>
> I admit that I haven't read this whole thread but:
>>
>> Using Apache Fast-CGI, you are going to fork a process for each
>> instance of the function being executed and that in turn will use
>> all CPUs up to the max available resource.
>>
>> With PostgreSQL, that isn't going to happen unless you are running
>> (at least) 8 functions across 8 connections.
>>
>>
>> Well, right, which is why I mentioned "even with dozens of clients."
>> Shouldn't that scale to at least all of the CPUs in use if the function
>> is CPU intensive (which it is)?
>>
>
> In theory but that isn't PostgreSQL that does that, it will be the kernel
> scheduler. Although (and I am grasping at straws):
>
> I wonder if the execution is taking place outside of the backend proper
> or... are you using a pooler?
>

No pooler, and the functions were in an ordinary SQL extension .so library
and loaded as

CREATE OR REPLACE FUNCTION funcname( ... ) returns ...
AS 'libxxx.so', 'funcname LANGUAGE c STRICT IMMUTABLE COST 10000;

Craig

> JD
>
>
>
>> Craig
>>
>>
>>
>>
>> JD
>>
>> --
>> Command Prompt, Inc. - http://www.commandprompt.com/ 503-667-4564
>> PostgreSQL Centered full stack support, consulting and development.
>> Announcing "I'm offended" is basically telling the world you can't
>> control your own emotions, so everyone else should do it for you.
>>
>>
>>
>>
>> --
>> ---------------------------------
>> Craig A. James
>> Chief Technology Officer
>> eMolecules, Inc.
>> ---------------------------------
>>
>
>
> --
> Command Prompt, Inc. - http://www.commandprompt.com/ 503-667-4564
> PostgreSQL Centered full stack support, consulting and development.
> Announcing "I'm offended" is basically telling the world you can't
> control your own emotions, so everyone else should do it for you.
>

--
---------------------------------
Craig A. James
Chief Technology Officer
eMolecules, Inc.
---------------------------------