Re: autovacuum multiworkers, patch 5

> > >Yes, that's correct.  Per previous discussion, what I actually wanted to
> > >do was to create a GUC setting to simplify the whole thing, something
> > >like "autovacuum_max_mb_per_second" or "autovacuum_max_io_per_second".
> > >Then, have each worker use up to (max_per_second/active workers) as much
> > >IO resources.
>
> One thing I forgot to mention is that this is unlikely to be implemented
> in 8.3.

This is a WIP cost balancing patch built on autovacuum-multiworkers-5.patch.
The total cost of workers are adjusted to autovacuum_vacuum_cost_delay.

I added copy of worker's cost parameters to the shared WorkerInfo array.
A launcher and each worker reads and writes the copied parameters when
a worker starts a vacuum job or exit the process. Workers assign their local
VacuumCostDelay from the shared value every sleep in vacuum_delay_point().

I agree that "mb_per_second" or "io_per_second" are easier to use than
present cost delay parameters, but we need more research to move to it.
I think it is better to keep "cost_limit" and "cost_delay" as of 8.3,
but we need cost-balanced multiworkers at any rate.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center