Groups > comp.lang.java.programmer > #6887

Re: A quota based lock

From	Eric Sosman <esosman@ieee-dot-org.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: A quota based lock
Date	2011-08-08 20:41 -0400
Organization	A noiseless patient Spider
Message-ID	<j1pvpg$20h$1@dont-email.me> (permalink)
References	(2 earlier) <j1p40f$jua$1@dont-email.me> <j1p4n8$pog$1@dont-email.me> <j1pago$8ua$1@dont-email.me> <j1pbj1$hvd$1@dont-email.me> <9aasp0F9v2U1@mid.individual.net>

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On 8/8/2011 3:46 PM, Robert Klemme wrote:
> On 08.08.2011 20:57, markspace wrote:
>> On 8/8/2011 11:39 AM, Knute Johnson wrote:
>>
>>> No priority scheme will ever be truly fair. I'll bet you could get
>>> pretty close without being too complicated. I'll think about it some
>>> more.
>>
>>
>> A simple priority system might involve multiple queues, where the high
>> priority queues are serviced X times more than the lower ones.
>>
>> E.g., two queues. Queue A gets 10 jobs executed for each 1 job that
>> queue B gets executed. But because queue B is always guaranteed to be
>> serviced eventually, there is no starvation.
>>
>> This is a simple step up from round-robin service (which is what Eric
>> proposed). There are many algorithms existing. Check out any text on OSs
>> and job scheduling.
>
> Another idea would be to take the time a task has access to the
> resource, sum up per task category and for the next task pick the first
> one from the category which is furthest below its specified share
> (percentage). Basically your approach measures executions and this
> approach measures actual resource usage time.

     Yes, all these disciplines are plausible.  My main piece of advice
is KISS: Begin with the simplest possible solution, and elaborate it
only when there's solid evidence it won't suffice.

     Sometimes the evidence can be gathered in advance: If you know
things about arrival rates and hold times and latency requirements, you
may be able to do a calculation that shows simple FIFO won't hack it.
More often, given the inherent complexity and "brittleness" of software
systems, you'll need to implement first and measure afterwards to learn
about a solution's shortcomings.  This can lead to discarding the first
solution -- but, hey: It was the simplest one you could imagine, so you
probably didn't expend inordinate effort on it, right?  Much cheaper to
jettison a simple approach than a complicated one.

     KISS.

-- 
Eric Sosman
esosman@ieee-dot-org.invalid

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Thread

A quota based lock Robert Stark <panxiaozhong@gmail.com> - 2011-08-08 00:13 -0700
  Re: A quota based lock Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-08 07:58 -0400
    Re: A quota based lock Knute Johnson <september@knutejohnson.com> - 2011-08-08 09:48 -0700
      Re: A quota based lock markspace <-@.> - 2011-08-08 10:00 -0700
        Re: A quota based lock Knute Johnson <september@knutejohnson.com> - 2011-08-08 11:39 -0700
          Re: A quota based lock markspace <-@.> - 2011-08-08 11:57 -0700
            Re: A quota based lock Robert Klemme <shortcutter@googlemail.com> - 2011-08-08 21:46 +0200
              Re: A quota based lock Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-08 20:41 -0400
                Re: A quota based lock Robert Klemme <shortcutter@googlemail.com> - 2011-08-10 09:36 +0200
                Re: A quota based lock Robert Stark <panxiaozhong@gmail.com> - 2011-08-10 04:40 -0700
                Re: A quota based lock Robert Klemme <shortcutter@googlemail.com> - 2011-08-10 18:55 +0200
                Re: A quota based lock Martin Gregorie <martin@address-in-sig.invalid> - 2011-08-10 19:26 +0000
                Re: A quota based lock Patricia Shanahan <pats@acm.org> - 2011-08-10 12:37 -0700
                Re: A quota based lock Robert Stark <panxiaozhong@gmail.com> - 2011-08-10 18:30 -0700
                Re: A quota based lock markspace <-@.> - 2011-08-10 19:17 -0700
                Re: A quota based lock Robert Klemme <shortcutter@googlemail.com> - 2011-08-11 12:32 +0200
          Re: A quota based lock Tom Anderson <twic@urchin.earth.li> - 2011-08-09 21:00 +0100
  Re: A quota based lock markspace <-@.> - 2011-08-08 07:58 -0700
  Re: A quota based lock Tom Anderson <twic@urchin.earth.li> - 2011-08-09 21:45 +0100

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