[Swift-devel] excessive rate throttling for apparently temporally-restricted failures

[Mihael Hategan]

For some reason this quote from that article seems particularily
relevant (in that it shows how similar the problem is):

A simple way to implement cruise control is to lock the throttle
position when the driver engages cruise control. However, on hilly
terrain, the vehicle will slow down going uphill and accelerate going
downhill. This type of controller is called an open-loop controller
because there is no direct connection between the output of the system
(the engine torque) and its input (the throttle position).

In a closed-loop control system, a feedback controller monitors the
output (the vehicle's speed) and adjusts the control input (the
throttle) as necessary to keep the control error to a minimum (to
maintain the desired speed). This feedback dynamically compensates for
disturbances to the system, such as changes in slope of the ground or
wind speed.


On Sun, 2007-10-28 at 22:48 -0500, Ioan Raicu wrote:
> Right, I now remember reading that... too many emails, and our
> discussion got side-tracked :)
> Thanks for the control theory link, it looks like a good read!
> 
> Ioan
> 
> Mihael Hategan wrote: 
> > On Sun, 2007-10-28 at 22:41 -0500, Ioan Raicu wrote:
> >   
> > > If the knobs are all there, then I don't think there is an issue at
> > > the moment.  I think this all started by Ben saying that there was
> > > excessive throttling due to the site scoring.  Understanding how to
> > > fix the site scoring is one thing.  Being able to disable site scoring
> > > is another, which seems to be there already.  Ben, can you turn site
> > > scoring off, and see if that solves your problem for now?
> > >     
> > 
> > You can re-read Ben's earlier answer to your same question. I'll post it
> > here:
> > 
> >   
> > > I know how to disable it. I don't particularly want it running rate free.
> > > 
> > > Whats happening here is that the feedback loop feeding back too much / too 
> > > fast for the situation I experience.
> > > 
> > > There's plenty of fun to be had experimenting there; and I suspect there 
> > > will be no One True Rate Controller.
> > > 
> > > 
> > >     
> > 
> > 
> > 
> >   
> 
> -- 
> ============================================
> Ioan Raicu
> Ph.D. Student
> ============================================
> Distributed Systems Laboratory
> Computer Science Department
> University of Chicago
> 1100 E. 58th Street, Ryerson Hall
> Chicago, IL 60637
> ============================================
> Email: iraicu at cs.uchicago.edu
> Web:   http://www.cs.uchicago.edu/~iraicu
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