Debugging and resolving high loadavg when running MailScanner

Wed Feb 16 13:42:33 GMT 2005

Excuse me, but why are you "hung up" on loadfactor as a performance
meter?
It is just the average run queue size (averaged over 1, 5 and 15
minutes), and as such is meant
to vary.

You say you have a 2 CPU system, in which case (with a "SMP capable"
kernel) you'd be fine
with anything up to 2 in a "sustained load" (meaning more than in
transient peaks).

Add to this that processes in "non-interruptible wait" (usually for IO
resources) add an unconditional
1 (one) each, it is not at all surprising that the load goes a bit beyond
your "CPU count" when you
have a larger batch of messages coming in.

Unless you perceive true slowdowns, you don't really have a problem
with that.

Now, the swap bit _could_ be an indicator of true problems... You say you
use it for other things than
as a mailhub... So you might be in a slightly memory starved state,
easily determined via vmstat or sar,
if you have a fair amount of ongoing swapping.
But using swap on a system that runs for an extended period of time is
usually not an indicator of
problems in and of itself, it is the actual moving to/from swap of
frequently used memory slices that'll
be a killer.
If you can determine that you have this situation, you have only two
venues: reduce the RAM usage
(by reducing what the machine does), or add more RAM.

Nothing you've said so far indicate that you do have a problem... Does
the machine occasionally
slow down in a perceptible and measurable way? Does MailScanner report
huge batches?

I'd like to recommend the excellent "swordfish book" from o'rielly
(Systems performance tuning).
Even though it is geared toward Solaris primarily and linux (2.4)
secondarily, it has a lot of general
good tips (and tool usage tips that are rather generic for most unices).

-- Glenn
-----Original Message-----
From: MailScanner mailing list [mailto:MAILSCANNER at JISCMAIL.AC.UK]
On Behalf Of Richard Curtis
Sent: den 16 februari 2005 13:04
To: MAILSCANNER at JISCMAIL.AC.UK
Subject: Re: Debugging and resolving high loadavg when running
MailScanner

I am not using either... running
spamassassin -D --lint -p
/etc/MailScanner/spam.assassin.prefs.conf  says there are two
problems - but the two problems appear to be that razor and pyzor
are not installed..

The load is sitting at around 0.5 at the moment - but when I was
looking about 5 minutes ago it shot to 5.0 when a large batch of
email came in.
I am wondering if I need to do something with the number of
children.  I currently have it set to 10 - based on the
reccomendation of 5 per cpu.  
The other thing I think might be related to my problems are the
fact that the system is using a fair amount of swap - would that
contribute to the load ?

Rich 
Are you using razor or pyzor in that setup and does

  spamassassin -D --lint -p
/etc/MailScanner/spam.assassin.prefs.conf

show any problems with either of these?

If so,

  razor-admin -discover
  pyzor discover

might be useful (I've put them in a cron job here).

Cheers,

Phil

----
Phil Randal
Network Engineer
Herefordshire Council
Hereford, UK

________________________________________________________________________________
From: MailScanner mailing list
[mailto:MAILSCANNER at JISCMAIL.AC.UK] On Behalf Of
Richard Curtis
Sent: 16 February 2005 11:33
To: MAILSCANNER at JISCMAIL.AC.UK
Subject: Debugging and resolving high loadavg when
running MailScanner

Hi All,
  I have been running MailScanner (Version 4.35.11) for
some time, but over the last 2 -3 weeks, my loadavg has
gone from ~0.10-0.20 to as high as 4.  This may not
seem high to some, but as I have other services on this
box I want to try to reduce the load.
The box runs httpd, sendmail/MailScanner with clamav,
radius and pop.  There are multiple hosted domains on
the server. 
The box is a dual AMD Athlon MP 1200 with 512MB RAM. 

All mail is scanned through MailScanner for virus's,
but only a small number of the domains (low traffic
ones) have SpamAssassin enabled in MailScanners
configs.
I have to admit that I am a bit confused by some of the
MailScanner config options - for example, the effects
of "Deliver In Background = yes" and "Delivery Method =
batch".

By setting the delivery method to queue, what kind of
impact on delivery time can I expect ?  Will this have
a significant effect of lowering the load ?

One other question, I note from looking through the
logs, I see entries like:
Feb 16 11:25:32 lancelot MailScanner[7544]: New Batch:
Scanning 1 messages, 1720 bytes
Feb 16 11:25:32 lancelot MailScanner[7544]: MCP Checks
completed at 1720 bytes per second
Feb 16 11:25:32 lancelot MailScanner[7544]: Spam Checks
completed at 1720 bytes per second
Now what confuses me here is that I have MCP checks and
Spam checks set to off for this mail domain - so why
are the checks happening ?

Any suggestions on performance tuning of MailScanner,
or possible sendmail config tweaks would be greatly
appreciated.

Regards

Richard

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Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.8.8 - Release Date:
14/02/05

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No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.8.8 - Release Date: 14/02/05

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