Re: [pgsql-hackers] Daily digest v1.5943 (21 messages)

On Fri, 2006-05-19 at 13:41 -0300, pgsql-hackers-owner@postgresql.org
wrote:

> Marc Munro wrote:
> > Veil http://pgfoundry.org/projects/veil is currently not a very good
> > Postgres citizen.  It steals what little shared memory it needs from
> > postgres' shared memory using ShmemAlloc().
> >
> > 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.
>
> Why should this be individually restricted? AFAICS Veil's
> functionality
> would be essential to access row level ACL controlled tables, so if
> it
> fails for low mem conditions it's much like a backend failure.

The problem is that postgres currently has no way of knowing how much
shared memory Veil is likely to require, and so will not allocate space
for it.  Consequently if Veil needs a lot of shared memory, it is
unlikely to be able to get it.

My intention is to allow add-ins to use only shared memory that has been
allocated for their own use, to ensure that enough has been allocated,
to isolate postgres shared memory from abuse by add-ins, and to avoid
the need for add-ins to manage their own shared memory.

__
Marc