[comp.mail.sendmail] sendmail 5.61 vs the nameserver

brian@ucsd.EDU (Brian Kantor) (05/18/89)

I recently installed sendmail 5.61, and after a week of incredibly bad
performance, went back to 5.60 while I figure out what's going wrong.

The problem was that our throughput dropped tremendously.  We have only
a Vax-750, which you might optimistically rate at .75 MIP, and the new
sendmail seemed to make the system run quite a bit slower.

I suspect that it is 5.61's interaction with the nameserver that causes
this.  We have it configured with the NO_WILDCARD_MX option set, which
causes it to do a C_ANY call on the nameserver instead of a C_CNAME.  I
believe the theory behind doing this was that by making such a call, the
local nameserver would cache all the data for the hostname being looked
up, which would save a second reference across the internet for the
common case where an MX lookup is followed by an A lookup for the same
host.

However, this also causes WKS, HINFO, and every bloody thing else known
about that host to get transferred too, and we have observed that the
memory working set of the bind nameserver with 5.61 was much larger than
with 5.60 which didn't do C_ANY.  In fact, it got larger than our
available physical memory, which means that the poor little 750 was
paging for a good percentage of the mail passing through.

I have yet to try 5.61 with the C_ANY disabled, as it took us several
days to recover from the previous misadventure and I'm not anxious to go
through that again.

Does anyone have any ideas about this sort of interaction?  Or is there
simply some bugfix for 5.61 that'll correct this situation?

	Brian Kantor	UCSD Office of Academic Computing
			Academic Network Operations Group  
			UCSD C-010, La Jolla, CA 92093 USA
			brian@ucsd.edu ucsd!brian BRIAN@UCSD