Re: [v9.1] sepgsql - userspace access vector cache

> On Wed, Jul 20, 2011 at 12:40 PM, Kohei Kaigai
> <Kohei(dot)Kaigai(at)emea(dot)nec(dot)com> wrote:
> > One question is why InitCatalogCache() should be invoked from InitPostgres()?
> > If we initialize syscache on starting up postmaster process, I think
> > all the syscache buckets will be ready on child process forks, and
> > unused syscache does not consume physical memory, even if security
> > label acquire 2048 of buckets.
>
> Most of the overhead seems to be the cost of the page faults required
> for the kernel to map the relevant pages into the process address
> space. After a fork(), all those pages become copy-on-write, so if
> the syscaches are actually used this doesn't save much of anything.
> In the specific case of sepgsql it would help, though, because what
> you're proposing is to add a syscache that will in most cases never be
> accessed at all. We'd still have a problem in the EXEC_BACKEND (i.e.
> Windows) case, however...
>
Hmm. It might not work in windows case.

I'd like to have a discussion about syscache towards next commit-fest.
The issues may be:
- Initial bucket allocation on most cases never be referenced.
- Reclaim cache entries on growing up too large.

Thanks,
--
NEC Europe Ltd, SAP Global Competence Center
KaiGai Kohei <kohei(dot)kaigai(at)emea(dot)nec(dot)com>