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One thing that I noticed is that the site score is quick to react to
failed jobs, but slow to react to successful jobs, to the point that
things take a long time to recover once some rough waters were
encountered. Using the car analogy from below, it would be like coming
to a downward slope where the cruise control adjusts the throttle
position from say 25% to 5% while on the downward slope, but then when
it gets back on flat ground, not going back to 25% for a long time due
to the previous downward slope. Basically, I think the algorithm
memory might need some tunning, maybe using a window based memory (as
opposed to the entire history of memory), or perhaps give higher weight
to more recent events, weight events according to their execution
times, reward more successive good jobs to allow the system to get back
a high score faster if jobs keep completing successfully, etc...
certainly lots of things to try out!<br>
<br>
Mihael Hategan wrote:
<blockquote cite="mid:1193629988.888.12.camel@blabla.mcs.anl.gov"
type="cite">
<pre wrap="">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:
</pre>
<blockquote type="cite">
<pre wrap="">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:
</pre>
<blockquote type="cite">
<pre wrap="">On Sun, 2007-10-28 at 22:41 -0500, Ioan Raicu wrote:
</pre>
<blockquote type="cite">
<pre wrap="">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?
</pre>
</blockquote>
<pre wrap="">You can re-read Ben's earlier answer to your same question. I'll post it
here:
</pre>
<blockquote type="cite">
<pre wrap="">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.
</pre>
</blockquote>
<pre wrap="">
</pre>
</blockquote>
<pre wrap="">--
============================================
Ioan Raicu
Ph.D. Student
============================================
Distributed Systems Laboratory
Computer Science Department
University of Chicago
1100 E. 58th Street, Ryerson Hall
Chicago, IL 60637
============================================
Email: <a class="moz-txt-link-abbreviated" href="mailto:iraicu@cs.uchicago.edu">iraicu@cs.uchicago.edu</a>
Web: <a class="moz-txt-link-freetext" href="http://www.cs.uchicago.edu/~iraicu">http://www.cs.uchicago.edu/~iraicu</a>
<a class="moz-txt-link-freetext" href="http://dsl.cs.uchicago.edu/">http://dsl.cs.uchicago.edu/</a>
============================================
============================================
</pre>
</blockquote>
<pre wrap=""><!---->
</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
============================================
Ioan Raicu
Ph.D. Student
============================================
Distributed Systems Laboratory
Computer Science Department
University of Chicago
1100 E. 58th Street, Ryerson Hall
Chicago, IL 60637
============================================
Email: <a class="moz-txt-link-abbreviated" href="mailto:iraicu@cs.uchicago.edu">iraicu@cs.uchicago.edu</a>
Web: <a class="moz-txt-link-freetext" href="http://www.cs.uchicago.edu/~iraicu">http://www.cs.uchicago.edu/~iraicu</a>
<a class="moz-txt-link-freetext" href="http://dsl.cs.uchicago.edu/">http://dsl.cs.uchicago.edu/</a>
============================================
============================================</pre>
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