SCHEDULE and high load situations

Martin Blapp mb at
Wed Aug 11 11:10:45 PDT 2004


> You might well want to try 4BSD.

I did that too. The milter stress test I run was sending 200 mails
with 5 different sorts of attachements into a mail loop. This means
these 200 mails are going 26 times trough the milter.

The ULE scheduler did process them first very fast. With more processes,
the sendmail transactions lagged a lot and it was only running 1-2 of
them at one time. This sucks because there is also a lot of timeout
handling (waiting for DNS responses).

All in one I must say that the SCHED4BSD processed the mails in half of
the time as SCHEDULE did. The mix involved included everything:

- Preforked mimedefang workers
- Forked Sendmails
- Threaded applications like clamd, mimedefang-milter

So I'd call it a typical real world situation.

Another thing I observed was that SCHED4BSD has zero IDLE time, while
SCHEDULE always idled between 20% and 50% ! This with 500 running processes
and a load of 2.5 -3.0.


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