barmar at alum.mit.edu
Tue Oct 5 12:07:47 UTC 2004
In article <cjthjq$11lh$1 at sf1.isc.org>,
"Walkenhorst, Benjamin" <Benjamin.Walkenhorst at telekom.de> wrote:
> Hello everyone,
> In what respect is BIND's behaviour affected by the value of
> BIND will look through its cache every <cleaning-interval> minutes (default:
> 60) for expired entries and, if it finds any, removes them, that much I could
> find out in the manual.
> But what happens when an already expired entry is requested again, before
> being removed from cache? Will the server remove it just then (and probably
> re-query the RR)? This seems like the only sane behaviour I could come up
> with for this situation, so ... could someone confirm to me BIND does behave
> like this? (The alternative looks like passing expired RRs to resolvers which
> just seems silly).
Yes, that's what it does. In fact, in early versions of BIND this was
the *only* way that expired entries would be cleaned up.
> In what respect will modifying this value change the behaviour of the system?
> Will it just make BIND free up (de facto unused) memory faster (or slower,
> depending on how I change the value) or are there other effects to be
That's all it does.
> If I am not entirely mistaken, the machines BIND runs on have... sufficient
> memory at least, so just _saving_ some won't be a big deal. On the other
> hand, we have to use BIND 9.1.1 right now which apparently doesn't implement
> a 'max-cache-size' option. So with that unavailable, could I use the
> 'cleaning-interval' for controlling - or at least influencing - the memory
> usage of BIND?
> Would setting this value too low (say, 1) adversely influence BIND's
> performance? (Like if it has a big cache, it might have to go all over it
> again and again...)
Yes. You'll be wasting lots of time, since the cache won't have grown
very much, and few entries will have expired since the last cleanup.
Barry Margolin, barmar at alum.mit.edu
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