Re: bg worker: general purpose requirements

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