max-cache-size (was: no subject)

Evan Hunt Evan_Hunt at
Tue May 27 20:15:05 UTC 2008

> Hmmm... how to reconcile this with the previous reports on bind-users 
> of memory usage mushrooming out of control in 9.5.0 alpha/beta releases?
> Have those been satisfactorily resolved now?

That issue wasn't related to cache performance.  It's a bug that would
show up on authoritative servers handling a very large number of zones,
especially if they also use large ACLs--the people who've reported it had
tens to hundreds of thousands of zones, and ACLs with thousands of elements.

The problem was that zone ACLs (allow-transfer, allow-notify, allow-query,
etc) were being copied into each zone rather than loaded into memory once
and then referenced by the zones that use them.  That adds up after a while.

Regrettably, the problem was noticed too late in the test cycle for a fix
to be included in 9.5.0 (which we expect to be public in a few more days).
A patch will be included in the KNOWN-DEFECTS file (read: "not tested to
ISC's official satisfaction; use at your own risk--but I, the author,
personally believe it to be solid").  After more thorough testing it'll
be incorporated into 9.5.1.

Caching resolvers shouldn't be affected at all.  Authoritative servers
with a smaller number of zones will be affected but it won't bother them
much.  People running authoritative servers with huge numbers of zones
who are brave enough to use a point-zero release in the first place are
hopefully brave enough to risk the KNOWN-DEFECTS patch. :)

Cache performance should be improved regardless.

Evan Hunt -- evan_hunt at
Internet Systems Consortium, Inc.

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