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From: bass@dmsd.UUCP (John Bass)
Newsgroups: net.arch
Subject: Re: Magic Cookies and File Systems
Message-ID: <171@dmsd.UUCP>
Date: Mon, 11-Mar-85 18:01:27 EST
Article-I.D.: dmsd.171
Posted: Mon Mar 11 18:01:27 1985
Date-Received: Thu, 14-Mar-85 03:42:15 EST
References: <917@sjuvax.UUCP> <538@rlgvax.UUCP>, <190@u1100s.UUCP> <302@cmu-cs-spice.ARPA>
Lines: 34

From Mr Tevanian:
	"Would you care to say *why* the file system is the only logical
	place for global names to reside? .. In fact, THERE IS NO REASON
	that the kernel need know what a file is! Of course, many of the
	readers of this newsgroup (hopefully not all) are still living in
	the primitive world of "the Unix Way."

More Ivory Tower snobbery we can do with out ... every CSc department has
its pet students and operating system research programs to produce mindless
trash to be ignored by the rest of the sane world (how this for an attention
getter living in the primative world). OS research is the fabric of learning
what and what not do do in real life -- more the latter I feel. I will grant
him that an OS NEED NO KNOW about a file as a fundamental resource for some
applications -- on the other hand the file is the basis of most commercial
applications environments.

From the abstract point of view nami in UNIX provides the mapping from
a character string name space to a resource ID (an inode). A resource
ID in my model of lockf/locking is a semaphore point with a large number of
magic cookies in it. Of course most resource ID's are files, but others are
network interfaces, system services, drivers, etc. It is unfair to say that
every unix file descriptor is a file.

As for performance you quote for PV operations ... the lockf call operates
on a 780 with similar timings -- thus there is nothing particularly sloooow
about locking and semaphores done with inode handles.

Path/file names are a good (if not best) way of describing resource IDs --
the magic number approach is trash ---

-- 
John Bass
DMS Design (System Performance and Arch Consultants)
{dual,fortune,idi,hpda}!dmsd!bass     (408) 996-0557