| > queue_run_max Use: main Type: integer Default: 5
| > This controls the maximum number of queue runner processes that an Exim
| > daemon can run simultaneously.
|
| -> as written: the maximum number of parallel running Exims processing
| the current mail queue. This number is independend on the load of your
| system. As each process locks one message, it's the maximum number of
| of messages delivered at the same time. (Not the maximum number of
| deliveries, as each message may have several recipients, which Exim
| may deliver to in parallel.)
queue_run_max is not quite the maximum number of simultaneous
deliveries that Exim may ever be doing at once, because it only limits
*queue runners*. Exim load and load limiting is complicated because Exim
can deliver email both from queue runners *and* immediately when the
email is submitted. So you can have some number of queue runners (up to
queue_run_max) and also some number of immediate delivery processes.
Years ago I tried to write down everything I had worked out about
Exim load limiting. I think that nothing substantial has changed
since 2008 when I did this and the following is still relevant if
people want lots of detail:
http://utcc.utoronto.ca/~cks/space/blog/sysadmin/EximLoadLimiting
(If things have changed I'd love to hear about it.)
- cks
