Re: [exim] number of named lists default

On Sun, 7 Jan 2007, Jethro R Binks wrote:

> I've always thought that the default of 16 named lists to be rather low;
> in testing a new configuration, I've found I'm now using more than that.

I'm always very bad at guessing how many of anything people will
actually use in practice.

> Could I suggest an increase to the default in the source, to 32? Or is
> more than 16 named lists unusual? Is there a notable cost in increasing
> it?

I think it is unusual, because nobody else has raised this before. There
is a notable cost because the caching arrangements use bitmaps, 2 bits
per list. There are two caches for each address (local part + domain).
Thus, increasing to 32 would add 8 bytes in the data block that is used
for each and every address. A message with 1000 addresses would use up
another 8K of memory.

I'm always cautious about increasing the size of that data block.
Probably overly so, but I come from the days when memory was expensive.

> I know I can change it myself at compile time, but I use the FreeBSD port,
> and there is currently no facility provided to make that change. I am
> chatting to the port maintainer about it anyway, but I think a change to
> the source default would be generally beneficial.

I think it would be worth discussing this on one of the mailing lists to
see whether there is any general feeling that 16 is too small. I would
be happier to see it left as it is by default - clearly having a way to
adjust it for FreeBSD would be useful.


Philip

--
Philip Hazel, University of Cambridge Computing Service.