From: Joshua D. Drake <jd@commandprompt.com>
To: Craig James <cjames@emolecules.com>
Cc: Graeme B. Bell <graeme.bell@nibio.no>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Hmmm... why does CPU-intensive pl/pgsql code parallelise so badly when queries parallelise fine? Anyone else seen this?
Date: Wed, 08 Jul 2015 10:52:08 -0700
Message-ID: <559D6348.6000508@commandprompt.com> (raw)
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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?
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.
> ---------------------------------
--
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To: pgsql-performance@postgresql.org
Cc: jd@commandprompt.com, cjames@emolecules.com, graeme.bell@nibio.no
Subject: Re: Hmmm... why does CPU-intensive pl/pgsql code parallelise so badly when queries parallelise fine? Anyone else seen this?
In-Reply-To: <559D6348.6000508@commandprompt.com>
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