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From: phil@amdcad.UUCP (Phil Ngai)
Newsgroups: comp.arch
Subject: caches and the kernel
Message-ID: <14362@amdcad.UUCP>
Date: Sun, 18-Jan-87 01:25:39 EST
Article-I.D.: amdcad.14362
Posted: Sun Jan 18 01:25:39 1987
Date-Received: Sun, 18-Jan-87 07:40:29 EST
Organization: AMDCAD, Sunnyvale, CA
Lines: 21

Several people have told me that although it is hard to simulate (one
person suggested using a logic analyzer to get address traces), it
does seem to be the case that the Unix kernel does not interact with
caches as well as applications such as nroff. This led me to wonder if
in that case, one might not do well to turn off the cache while the
processor is in supervisor mode, since the hit rate does not seem to
be very high and you thereby avoid flushing the cache of information
that is useful to the application. This assumes the kernel was entered
through a system call and returned to the same process. If a new
process was run, then 1) the cache would probably have to be much
larger and 2) process switches probably happen at a rate low enough
that it doesn't matter if the cache is invalidated. Anyway, these are
just guesses and I would like to invite discussion on this subject.

-- 
 Warning: the California AAA is pursuing a policy which would spend 
 gasoline taxes on mass transit instead of roads.

 Phil Ngai +1 408 749 5720
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