Fellow PLUGgers,
I have been perpetually plagued with excessive modprobe scans during
uvscan startup, which is quite frequent as AMaViS calls uvscan once for
each email that passes through our system. This morning I kicked the
server up to life from a few hours of building-wide blackout, and it
suffered the usual flood of mail from our backup mail exchange. Without
much mail to read, I decided to give figuring out the root of this
matter another shot.
It turns out these modprobes (for stuff like /dev/hdX and /dev/sdX that
don't exist) are not directly caused by uvscan, but are instead caused
by DevFS in response to queries from uvscan. Why uvscan keeps scanning
for these devices is beyond me, and since it's not open source, there's
not much digging we can do there.
One tip available online was to add the following lines to
/etc/modules.conf:
alias block-major-8 off
alias block-major-22 off
alias block-major-33 off
alias block-major-34 off
I guess these are good (eg: they're still in my /etc/modules.conf), but
they honestly didn't do much to help. AMaViS already runs uvscan using
"--secure -rv --summary --noboot", so I don't think there's much
tweaking that can be done there, either.
What finally fixed things was disabling DevFS's automatic module loading
feature, by commenting out the following line from /etc/devfsd.conf:
LOOKUP .* MODLOAD
This is present on at least Debian Sid machines, but should be the
default on most other distributions as well. With this feature turned
off and DevFS restarted, uvscan doesn't cause DevFS to do expensive
modprobes anymore, and mail throughput has gone up considerably. This
is, of course, at the expense of not being able to access /dev/foo and
in turn getting foo.o autoloaded. This doesn't seem to be too harsh an
impact on our server, though. The only modules it needs are for
lm-sensors, and those aren't loaded by DevFS.
Just in case this comes in handy for anyone. :)
--> Jijo
--
Federico Sevilla III : http://jijo.free.net.ph : When we speak of free
Network Administrator : The Leather Collection, Inc. : software we refer to
GnuPG Key ID : 0x93B746BE : freedom, not price.
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