Re: Shared Memory Sizing

On Thu, 27 Jun 2002, Jan Wieck wrote:

> Can you please enlighten us what the optimum is? And please don't escape
> into the mmap solution if you cannot give that answer in diff format.

Well, first of all, let me note that this is all theoretical work on my
part so far. If someone is actually doing some real testing of this, I'd
be interested in the results. If the results are different from what I
think they should be, something strange is going on.

But you can look back through my posts if you like and tell me if
you disagree with my analysis of why increasing shared memory
buffers is generally going to reduce performance.

The optimum will depend on the number of connections you have and the
type of workload you have. At this point, I'm not even sure about how to
go about determining precisely what would be better and worse; it would
be a lot of work. (Probably a lot more than it's worth, given the prices
of memory these days.)

I'd say, at a rough estimate, go for a number of buffers 2-3 times the
maximum number of connections you allow. Or less if you anticipate
rarely ever having that many connections.

cjs
--
Curt Sampson  <cjs@cynic.net>   +81 90 7737 2974   http://www.netbsd.org
    Don't you know, in this new Dark Age, we're all light.  --XTC