Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uflorida!haven!mimsy!chris
From: chris@mimsy.umd.edu (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: name lookup cacheing (was Directory compression)
Keywords: 4.3BSD
Message-ID: <26083@mimsy.umd.edu>
Date: 19 Aug 90 23:31:57 GMT
References: <7913@lynx.UUCP> <26078@mimsy.umd.edu> <38254@ucbvax.BERKELEY.EDU>
Distribution: na
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 17

In article <38254@ucbvax.BERKELEY.EDU> edward@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)
Domain:	chris@cs.umd.edu	Path:	uunet!mimsy!chris
	(New campus phone system, active sometime soon: +1 301 405 2750)