Re: New feature proposal

On Fri, 2006-05-19 at 13:41 -0300, pgsql-hackers-owner(at)postgresql(dot)org
wrote:
> On Thu, 2006-05-18 at 17:39 -0700, Marc Munro wrote:
>
> > For Postgres 8.2 I would like Veil to be a better citizen and use
> only
> > what shared memory has been reserved for postgres add-ins.
>
> How would Postgres ask the add-in how much memory it needs? How would
> the add-in know how much has been reserved for it? How would an add-in
> know whether it was the only add-in and whether it could take all of
> the
> allocation?

Postgres would not ask any add-ins how much they need, it would simply
allocate the extra amount defined in a GUC and not make that available
through the normal shared memory allocation mechanism.

The add-in would not "know" how much had been allocated to it, but could
be told through it's own config file. I envisage something like:

in postgresql.conf

# add_in_shmem = 0 # Amount of shared mem to set aside for add-ins
# in KBytes
add_in_shem = 64

in veil.conf

veil_shmem = 32 # Amount of shared memory we can use from
# the postgres add-ins shared memory pool

I think this is better than add-ins simply stealing from, and contending
for, postgres shared memory which is the only real alternative right
now.

__
Marc