Excerpts from Euler Taveira de Oliveira's message of mié oct 26 16:57:18 -0300 
> On 26-10-2011 16:14, Alvaro Herrera wrote:
> > Well, just increasing the number of workers would do nothing to solve
> > the problem, because the more workers there are, the slower they work.
> > The actual solution to the problem would be decreasing
> > autovacuum_vacuum_delay_cost, and/or related knobs.
> >
> Why not? You're saying that parallelizing the work won't help? As about 
> autovacuum_vacuum_cost_delay, don't you think that 20ms isn't small enough to 
> suggest decreasing instead of increasing the number of workers?

I am saying that if you have two workers running, they increase their
cost delay to 40ms internally.  If you increase the max to four, they
would run at an effective delay of 80ms.

> > Wasn't there some discussion recently on measuring the length of the
> > work queue, or something like that?
> >
> Yes, there is. As I said, it is an expensive and approximate measure. I'm not 
> saying that is not the right direction, I'm arguing that a hint is better 
> than 
> nothing. Right now the only way to know if it is out of workers is to query 
> pg_stat_activity frequently.

Well, I'm not saying there aren't other ways.

Álvaro Herrera <alvhe...@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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