Re: Linux max on shared buffers?

On Thu, Jul 11, 2002 at 06:04:20PM +0900, Curt Sampson wrote:
> On Thu, 11 Jul 2002, Martijn van Oosterhout wrote:
> > The other possibility would be to use mmap instead. That way you avoid the
> > double buffering altogether. Do you have any ideas about that?
>
> On this page
>
> http://archives.postgresql.org/pgsql-hackers/2002-06/threads.php
>
> there's a thread about "Buffer management", and I have some posts to that
> about using mmap. Unfortunately, I can't point out the exact posts, because
> the php that's generating these pages is probably missing an end table
> tag, and so the pages render as completely blank on Linux Netscape 4.78.

Yeah, I thought of the writeback issue also. I was thinking that you might
have to keep the current shared memory scheme for written pages but use mmap
for reading them in. Since the number of written pages is much smaller than the
number of read pages, you can avoid a lot of double buffering.

But that does increase complexity and possibly cause portability problems,
since that could make assumptions about how buffers, shared memory and mmaps
are shared.

Not totally straight forward. Needs more thought obviously.
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> There are 10 kinds of people in the world, those that can do binary
> arithmetic and those that can't.