Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!decwrl!pyramid!prls!mips!mash
From: mash@mips.COM (John Mashey)
Newsgroups: comp.unix.wizards
Subject: Re: Sun 4 \"KNEE\" Wars
Message-ID: <2356@winchester.mips.COM>
Date: 11 Jun 88 05:26:27 GMT
References: <16138@brl-adm.ARPA>
Reply-To: mash@winchester.UUCP (John Mashey)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 19

In article <16138@brl-adm.ARPA> weiser.pa@xerox.com writes:
>aglew@urbsdc.urbana.gould.com says:
>"I don't have Sun 4 source at hand right now, but if their scheduler
>is similar to the standard BSD scheduler a process coming out of
>a sleep may [*] have its priority boosted. ...[further explanation here...]"
>
>But this explanation doesn't explain why Sun's show this behavior and Vaxes
>don't, nor why Sun-3's, with 8 MMU contexts, show the knee at 8 fast sleepers,
>and Sun-4 with 16 MMU contexts show it at 16!

A VAX uses a TLB, whose user portion must be flushed upon each context
switch, i.e., in some sense, it has 1 context (although this is not
strictly the same kind of context, as it does not need to be mass
saved/restored).  Hence, there is no reason for a VAX to have a
MMU-related knee anywhere.
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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