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From: ralphw@IUS3.IUS.CS.CMU.EDU (Ralph Hyre)
Newsgroups: comp.arch
Subject: Re: Curb feelers (was: Cray architecture)
Message-ID: <1555@pt.cs.cmu.edu>
Date: 28 Apr 88 14:37:13 GMT
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In article <359@spar.SPAR.SLB.COM> malcolm@spar.slb.com (Malcolm Slaney) writes:
>In article <2087@gumby.mips.COM> earl@mips.COM (Earl Killian) writes:
>> My favorite cpu meter was on the MIT AI Lab PDP-10 in the mid 70's.
>> AI had about 20 bitmap screens connected to it, and could memory map
>> the frame buffers.  Thus your display had a 36-pixel bar in the corner 
>> that flashed on and off, showing when... you were getting cpu cycles.  
>
> For my money I still prefer the SunView approach.  I like a pointer that 
>quickly shows the average load.  It is just too hard to quantify the load 
>with load bars.  (I've also used the bar graph (load average vs. time)
>approach but I don't think it is as responsive.)
>
>On the other hand the LispM's also show bars for Garbage Collection and
>paging time so it is easier to judge how much time your process is not
>getting because of system overhead.
>
As I recall, the KTV system had high-persistence monitors, I could
imagine the user seeing the bar on all the time, especially in darkened
rooms, which was usually how it was.

You really want something that shows your process' share of CPU, not just
the 'system' average.

With appropriate kernel hooks, you could have a bar graph that moves up or down
depending on CPU state.  (each tick in user mode (or the user's program) bumps
up one, each tick in supervisor mode (~system time), bumps it down by one,
you'd be swapping or paging when it stopped blurring up and down :-)  [This is
a bit tricky in software, since the clock tick handler probably runs in 
supervisor mode, but it should be straighforward with external hardware.]
On a Sun, you could probably use the LED's on the CPU board for something 
similar.  

>P.S.  We could also talk about the (switching) power supply on my Sun
>that whines when the CPU gets busy.....
Yeah, I'm waiting for a music program to come across the net....
The FPA tests make the most interesting sounds.
-- 
					- Ralph W. Hyre, Jr.

Internet: ralphw@ius2.cs.cmu.edu    Phone:(412)268-{2847,3275} CMU-{BUGS,DARK}
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