When is it safe to adjust berkeley_cachesize?

[Ross Boylan]

I've returned to investigating why populating Cyrus 2.2 with UW's
mailutil is rather slow (20 or 30 messages/second).  One advice I've
seen is to tweak berkeley_cachesize.  When is it safe to do so?  Only
when creating a new database?  Only when cyrus is shutdown? On the
fly?

Any other advice on identifying the source of the bottleneck or
conducting tests would be great too.  I'm using the Debian package on
GNU/Linux, on hardware that is pretty good (SATA disk, P4) but
definitely not a server class machine.

I tried using oprofile, but didn't really know what to make of the
results.  In particular, I'm not sure how to tell (with it or anything
else) where something is blocked but idle, waiting for a resource.
It's hardly using any CPU, so that's not the problem.

Given these difficulties, I'm inclined to just try out some different
configurations (probably starting with the sync behavior of the
filesystem, which may mean I need something other than ReiserFS, which
I'm currently using) and see what happens.

Thanks.
Ross Boylan