Re: Dead Space Map version 2

"Jim C. Nasby" <jim(at)nasby(dot)net> wrote:

> > I'd like to add some kind of logical flavors to max_fsm_pages
> > and max_dsm_pages.
>
> In the meantime, I'm not sure if it makes sense to tie the FSM size to
> the DSM size, since each FSM page requires 48x the storage of a DSM
> page. I think there's also a lot of cases where FSM size will not scale
> the same was DSM size will, such as when there's historical data in the
> database.

I see. We need separate variables for FSM and DSM.

Here is a new proposal for replacements of variables at Free Space Map
section in postgresql.conf. Are these changes acceptable? If ok, I'd
like to rewrite codes using them.

# - Space Management -

managed_relations = 1000 # min 100, ~120 bytes each
managed_freespaces = 2GB # 6 bytes of shared memory per 8KB
managed_deadspaces = 8GB # 4KB of shared memory per 32MB

managed_relations:
Replacement of max_fsm_relations. It is also used by DSM.

managed_freespaces:
Replacement of max_fsm_pages. The meaning is not changed,
but can be set in bytes.

managed_deadspaces:
A new parameter for DSM. It might be better to be scaled
with whole database size.

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