name lookup cacheing (was Directory compression)

[Chris Torek]

In article <38254 at ucbvax.BERKELEY.EDU> edward at ucbarpa.Berkeley.EDU
(Edward Wang) writes:
>A result of a study I did a while ago is that failed lookups often
>repeat ... and caching this information brings the hit rate ... up
>quite a bit.  (The cache would contain files known not to exist.)
>My impression is that BSD does not do this.
>Does anyone here know why?

4.3BSD and 4.3BSD-Tahoe do not, but 4.3BSD-Reno does.  As to why... probably
because Kirk did not think to do it at first.  It is easy enough to add:
just make a cache entry with a nil inode/vnode pointer.  (The 4.3BSD code
panic's on such an entry, which provides an existence proof that none now
exist :-) .)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
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