Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!voder!pyramid!prls!mips!mash
From: mash@mips.COM (John Mashey)
Newsgroups: comp.arch
Subject: Re: RISC v. CISC (really, context-switching & windows)
Message-ID: <7187@winchester.mips.COM>
Date: 27 Oct 88 22:31:13 GMT
References: <156@gloom.UUCP> <310@lynx.zyx.SE> <332@pvab.UUCP> <15964@agate.BERKELEY.EDU> <23367@amdcad.AMD.COM> <16003@agate.BERKELEY.EDU> <6996@winchester.mips.COM> <313@auspex.UUCP>
Reply-To: mash@winchester.UUCP (John Mashey)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 29

In article <313@auspex.UUCP> guy@auspex.UUCP (Guy Harris) writes:
>>	Register window design (as in UCB) used certain kinds of programs
>>	to create the statistics to support the design. User programs
>>	often bounce around in a fairly shallow window-count.
>>	UNIX kernels are worse.  They often zoom up and down 10-12 levels
>>	very quickly, causing window faults like crazy.  I have to believe
>>	the SunOS folks have been working hard to tune for this.

>While I was at Sun, I don't remember there ever having been any effort
>to reduce the depth of the kernel call stack in order to speed things up
>on SPARC-based Suns.  (Remember, they have to make it run sufficiently
>fast on three architectures, not one - four, if you count 370/XA and
>compatibles, and even more, if you consider that a lot of Sun code is
>going into S5R4....)

I'm surprised that nobody was doing this.  Note, however, that this is
NOT the "standard UNIX optimized for SPARC" issue, i.e., although
squishing the call tree wouldn't particularly help the other architectures,
it wouldn't hurt them that much either, and it might help SPARC some.
Of course, no sensible software engineer would do terrible distortions to
the code to do this, but I can imagine where people might put some effort
into (machine-independent) level-squishing.
As usual, if Guy says it wasn't being done, it probably wasn't;
certainly my comment was speculation.
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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