Re: [Mailman-Developers] Mailman with sendmail = performance bottleneck
On Wed, 22 Nov 2000 00:13:14 -0600 Bob Tanner firstname.lastname@example.org wrote:
Quoting Chuq Von Rospach (email@example.com):
You need to go into your system, and set
SMTP_MAX_RCPTS = 10
I had it down to 50, but I'll give 10 a try. Thanks.
FWLIW I usually use either 5 or 10. Depending on your MTA (Historically I've been using Exim, recently moved to Postfix for non-MTA related reasons) and the distribution of your membership lists across domains this can significantly speed queue emptying speed.
BTW: I haven't checked and I don't have anything in my spools to check. Does Mailman currently pre-sort the RCPT_TO list by domain?
BTW I recently wrote the following in another forum on Postix and Exim:
--<cut>-- I've spent the last week or so playing with both fairly extensively. They're sweet systems. More interestingly the performance curves for both are remarkably similar once your mail loads become large (ie your spool is always active (mail to deliver)). The different mostly lies in the curve up to continual activity, and the curve as they approach saturation (mail is arriving more quickly than they can get rid of it on a near continual basis). Loosely, Postfix' initial curve is very steep, but they both reach similar delivery rates for the continually active point.
I've had some problems simulating sustained saturation (test networks et al), but Exim seems to be friendlier to the localhost in such circumstances. Exim appears to implicitly assume that such queue congestion is temporary and that given enough time things will slow down enough so it can empty the queue. As such its less interested in "get that damned mail out of here now" than it is in, "be nice to the local machine and get the mail out when you can". There are obvious problems with this if your loads stay at or above capacity for extended periods, but equally, its rather nice from an admin perspective for the local machine.
Postfix conversely seems to operate on the "get that mail out of here now", and can be rather brutal on the local host during that process. Postfix under sustained saturation makes for a very heavily loaded system. Depending on what else you are doing there, this may be a problem, or not. It is this nature however which gives it the steep attack on delivery rates as versus Exim. The fact that their sustained delivery rates are so similar at the end of that curve is the really interesting bit however. --<cut>--
Unfortunatly I didn't have time to keep careful metrics, and my process wasn't really rigorous enough for that either a I was just trying to get some basic parameters on their behaviour.
I think this should be an FAQ.
FAQ #2 states to turn off synchronous DNS resolution. Anyone know how to do this via sendmail's .mc files?
Sorry, no idea. I gave up sendmail 5 years ago.
J C Lawrence