Nigel Kukard wrote:

>I'm glad you making progress man. Your findings really help and will
>help alot of people looking for similar info in future.

OK, I think I now have this pinned down - so a summary.
At first I was getting MySQL errors in Postfix - leading to timeouts 
and very slow throughput. This would appear to have been something 
related to the versions of software running on the backend - I did a 
dist upgrade and those errors have gone.

After a hint from Nigel, I tried injecting queries directly into 
policyd using nc. At first the backend saturated at about 30 
queries/s with a fair amount of WIO time. After a bit of MySQL tuning 
AND turning off/down logging AND making sure all syslogging was async 
I got this up to over 60 queries/s with the CPU saturated and little 
WIO.

I then turned my attention back to my other machines. A quick bash 
loop to generate emails to lots of recipients (not real I'd point out 
!) gave me a limiting rate of about 2 recipients/s with the backend 
showing lots of idle time.
Today, I reconfigured some other boxes to route mail via this setup. 
Running the same script on multiple boxes resulted in the rate 
scaling linearly with the number of sending machines - ie 2 machines 
got 4 recip/s, 3 machines gave 6/s, and 4 machines could generate 8 
recip/s. I'm assuming this is something Postfix related at the 
machines I'm generating the traffic on.

Since this is more than our requirements I'll leave it at that for 
now. At some time I'll need to look into what's limiting that.

>What sort of CPU usage are you seeing from policyd vs. mysql?  policyd
>should only be restricted by your CPU processing power and your DB
>speed, and I've personally not managed to saturate the CPU portion and
>its always the DB speed that gets hit first it seems.

Under the above test, with 4 machines sending mails at 8 
recipients/second, the backend is running at something like 80% idle 
on a single Intel(R) Pentium(R) 4 CPU 2.80GHz.
-- 
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.
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