Hello,
We have an alphaserver 1000 running 4.0B, patch kit 8. It is
significantly overloaded, a problem we are attempting to remedy by finding
enough money to replace it. In the meantime, we are trying to make the
machine as usable as possible. The machine is primarily used as a POP
server, an SMTP relay (from within our domain only, of course), and a web
server (Gee, I wonder why it's overloaded...).
The problem is this: When the machine is under heavy load (read M-F, 8-5),
connections to the SMTP port are frequently being refused. I have not been
able to find any other services that are refusing connections, but of
course the refusals are intermittent and unpredictable.
Things I've tried:
I looked at the sendmail source, and saw that it is doing a
listen(socket,10) meaning that it only allows 10 waiting connections on the
socket. I increased the socket subsystem SOMINCON (and SOMAXCON) to 4096,
which should (If I'm reading the documentation right) set every socket to
allow 4096 waiting connections before refusing connections.
I looked at vmstat and netstat during heavy load times to see if we are
short on memory or are having network load problems. The answers were no
and no.
Things I'm trying now:
- doing anything I can to reduce the load on the system.
- investigating whether there is anything in patch kit 9 that addresses
similar problems
Questions:
Am I understanding the SOMINCON/SOMAXCON stuff correctly?
Are there any tradeoffs in further increasing these variables, as the
server tuning document recommends, to the maximum value of 65535, and is
there any hope of this having any effect?
What techniques can you recommend to delve into this problem deeper, for
example to see if the connections are being refused by sendmail rather than
by DU, etc.
Any other suggestions for diagnostics/remedies/info/anything ?
Thanks, and I'll summarize for the list.
-- - keith
--
Keith Piepho kap_at_uakron.edu
Technical Services (330) 972-6130
The University of Akron
Received on Wed Mar 03 1999 - 16:07:07 NZDT