pruning dcache.

Rogier Wolff (
Mon, 17 Nov 1997 11:02:28 +0100 (MET)

Bill Hawes wrote:
> >
> > Nov 13 21:15:32 amd kernel: d_alloc: 889 unused, pruning dcache
> I'm not sure what would have caused it, but the getattr call failing is
> probably for the linux/include directory. If the client can't do a
> getattr, it can't use the directory.

Bill, Every two days or so someone steps up and says "what are these
'pruning dcache' messages doing in my log?". I want to join the chorus.

On my system, it first said "3098 unused, pruning dcache" and then in
quick succession, it then had 3097 unused twice in a row. I want to
be assured that you don't have a "static" upper limit where you bump into
and because no "reduction" is possible, the frequency of bumping into the
limit goes up and up as nothing can be freed.

Netscape seems to exhibit this behaviour. I have a java application that
might need 20Mb of memory. However at 16Mb of memory "in use" Netscape
starts calling the garbage collector. At the moment that I really have
16Mb allocated, calling the garbage collector is all that gets done.

In this case, I have the impression that the dcache needs pruning whenever
too many entries become unused, but that if there is fragmentation you
cannot really clean up. If that happens, the "threshold for another prune
run" should be increased.

If in my case the "prune limit" would be "3100", and pruning reduced the
number of free entries to 3095, then the new limit should be at least a
few hundred higher.


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