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From: herbie@polaris.UUCP (Herb Chong)
Newsgroups: net.unix-wizards
Subject: Re: 4.2 scheduler (and CPU utilization)
Message-ID: <319@polaris.UUCP>
Date: Wed, 4-Dec-85 20:48:19 EST
Article-I.D.: polaris.319
Posted: Wed Dec  4 20:48:19 1985
Date-Received: Sat, 7-Dec-85 04:35:05 EST
References: <1360@wanginst.UUCP> <879@psivax.UUCP> <3043@sun.uucp>
Reply-To: herbie@polaris.UUCP (Herb Chong)
Distribution: net
Organization: IBM TJ Watson RC
Lines: 33
Summary: 

In article <3043@sun.uucp> guy@sun.uucp (Guy Harris) writes:
>Well, it *can* spend that much time in the kernel, depending on what you're
>doing.  30 to 50% isn't *that* high (I've heard MVS spends at least 50% of a
>370-family machine's cycles); the paper Berkeley put out on 4.2/4.3
>performance tuning indicated that 4.1 spent about 45% of its time in the
>kernel, 4.2 spent about 55% of its time there, and that they'd cut it back
>to 45% with their tuning.

to set the record straight, a properly configured and tuned MVS system
running flat out will spend between 5 and 15 percent of it's time in
the kernel or related system programs averaged over a 15 minute
interval.  a 4.2 bsd system properly configured and tuned will spend
about 25 to 35 percent of it's time executing in the kernel.  if you
are willing to live with 45 percent system time averaged over 15
minutes, your system is overloaded for good response.  from what i hear
though, most people prefer to run their 4.2 systems that way.  for a 4M
780, the 15 minute load average rising above 10 is a warning that
system limits are being reached.  any time the 1 minute load average is
over 14 for more than 30 seconds, the system is beginning to thrash.
kernel character echo at 9600 baud is noticeably slower and and almost
stops when it reaches about 20.

Herb Chong...

I'm still user-friendly -- I don't byte, I nybble....

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