Re: 8.1beta, SunOS and shmget

On Mon, Aug 29, 2005 at 11:30:46AM -0400, Tom Lane wrote:
> "Sergey E. Koposov" <math@sai.msu.ru> writes:
> > Yes, the decreasing of max_prepared_transaction helped (after some 
> > testing, I've found that the max_prepared_transactions=3 
> > max_connections=10  shared_buffers=20 was well enough to fit 1mb of 
> > shared memory)
> 
> 20 buffers ... ugh.  Obviously we are on the hairy edge of no longer
> functioning at all in 1MB shared memory.  I'm not sure there is a whole
> lot we can do about this, but it's a tad irritating that clog, subtrans,
> and multixact are eating the equivalent of about 16 buffers
> (nonconfigurable) while the main buffer pool is so badly starved.
> It'd be better to reduce their allocations.

8 buffers each, I think, no?  That's 32 buffers total.  Maybe we could
make them allocate them automatically based on shared_buffers, with a
ceiling of 8?

For example Min(8, ceil(2*log(shared_buffers))) seems to behave nicely.
That'd mean 3*4 = 12 buffers when shared_buffers is below 100; and 8*4 =
32 buffers when shared_buffers is above 10000.

-- 
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"La Primavera ha venido. Nadie sabe como ha sido" (A. Machado)