Re: Do we need a ShmList implementation?

Markus Wanner <markus@bluegap.ch> wrote:
> I'm wondering how you want to implement the memory allocation part
Based on the feedback I've received, it appears that the only sane
way to do that in the current shared memory environment is to
allocate a fixed size of memory to hold these entries on postmaster
startup.  To minimize the chance that we'll be forced to cancel
running transactions to deal with the limit, it will need to be
sized to some multiple of max_connections.
Obviously, if there were a dynamic way to add to the entries as
needed, there would be one less setting (hard-coded or GUC) to worry
about getting right.  Too low means transactions need to be
canceled.  Too high means you're wasting space which could otherwise
go to caching.  And of course, the optimal number could change from
day to day or hour to hour.
-Kevin