From: | Markus Wanner <markus(at)bluegap(dot)ch> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com>, PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: bg worker: general purpose requirements |
Date: | 2010-09-20 17:45:41 |
Message-ID: | 4C979DC5.4060505@bluegap.ch |
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Lists: | pgsql-hackers |
Robert,
On 09/20/2010 06:57 PM, Robert Haas wrote:
> Gee, that doesn't seem slow enough to worry about to me. If we
> suppose that you need 2 * CPUs + spindles processes to fully load the
> system, that means you should be able to ramp up from zero to
> consuming every available system resource in under a second; except
> perhaps on a system with a huge RAID array, which might need 2 or 3
> seconds. If you parallelize the worker startup, as you suggest, I'd
> think you could knock quite a bit more off of this, but why all the
> worry about startup latency? Once the system is chugging along, none
> of this should matter very much, I would think. If you need to
> repeatedly kill off some workers bound to one database and start some
> new ones to bind to a different database, that could be sorta painful,
> but if you can actually afford to keep around the workers for all the
> databases you care about, it seems fine.
Hm.. I see. So in other words, you are saying
min_spare_background_workers isn't flexible enough in case one has
thousands of databases but only uses a few of them frequently.
I understand that reasoning and the wish to keep the number of GUCs as
low as possible. I'll try to drop the min_spare_background_workers from
the bgworker patches.
The rest of the bgworker infrastructure should behave pretty much like
what you have described. Parallelism in starting bgworkers could be a
nice improvement, especially if we kill the min_space_background_workers
mechanism.
> Neat stuff.
Thanks.
Markus Wanner
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