Some interesting stuff from PLD

Russ Allbery rra at stanford.edu
Wed May 7 18:03:27 UTC 2008


Julien ÉLIE <julien at trigofacile.com> writes:

> I also forgot to mention:
>
> msgidcachesize is currently 10,000.  Is that enough nowadays?
>     "nnrpd(8) can cache the storage token associated with a Message-ID
>     and save the cost of looking it up in the history file; for some
>     configurations setting this parameter can save more than 90%
>     of the wall clock time for a session."

This one is fairly recent and probably still okay.  IIRC, it's mostly used
for NEWNEWS.

> overcachesize is only 15...  Shouldn't it increased?  64 ? 128 ? 256 ? 384 ?..
>     "INN will keep around and open that many recently written-to overview
>     files in case more articles come in for those newsgroups. The default
>     value is 15 (which is probably way too low if you have a large
>     number of file descriptors available)."

overcachesize is a tradeoff between open file descriptors and potential
cache benefits.  I'm not really sure where the tradeoffs lie for it.  The
best way of figuring it out would probably be to instrument the code a bit
more so that nnrpd and innd can report how many cache hits and misses it's
getting on the overview cache.

I expect that with a full-feed server, there probably isn't enough
locality in incoming articles for the overview cache to do you any good,
so it's mostly useful for nnrpd (I forget exactly how it's used in the
code).

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>

    Please send questions to the list rather than mailing me directly.
     <http://www.eyrie.org/~eagle/faqs/questions.html> explains why.


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