Date: Thu, 28 Jan 1999 13:07:08 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Duncan Barclay <dmlb@ragnet.demon.co.uk> Cc: hackers@FreeBSD.ORG, wes@softweyr.com, dyson@iquest.net, Kevin Day <toasty@home.dragondata.com> Subject: Re: High Load cron patches - comments? Message-ID: <199901282107.NAA11042@apollo.backplane.com> References: <XFMail.990128185136.dmlb@computer.my.domain>
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:Speaking as an electronic engineer who uses feedback in circuits all the
:time:
:
:One thing to watch out for when you have rate-feedback and a limiter is
:essentially designing a unstable or chaotic system. The limit acts as a
:non-linearity in the system feedback function which is usually a bad thing.
:Non-linearities will at best open the feedback loop and at worst cause it to
:thrash around like a mad thing. Similarly, if you have too many feedback loops
:(i.e. rate and number) the feedback can start to oscillate...
:
:These effects may not be visible because the time constants of the feedback
:systems are likely to be longer than the process creation rate.
:
:All of these are testable but it is easy to generate an unstable system by
:changing time constants.
:
:Duncan
Think of it as the current-sense (aka limiting) resistor in a switching
power supply.
-Matt
:---
:________________________________________________________________________
:Duncan Barclay | God smiles upon the little children,
:dmlb@ragnet.demon.co.uk | the alcoholics, and the permanently stoned.
:________________________________________________________________________
:
Matthew Dillon
<dillon@backplane.com>
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