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Date: Tue, 18 Jun 2002 13:50:26 -0400
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From: Chris Friesen <cfriesen@nortelnetworks.com>
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To: Rik van Riel <riel@conectiva.com.br>
Cc: David Schwartz <davids@webmaster.com>, rml@tech9.net, mgix@mgix.com,
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Subject: Re: Question about sched_yield()
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Rik van Riel wrote:
> 
> On Tue, 18 Jun 2002, Chris Friesen wrote:

> > However, if there is anything else other than the idle task that wants
> > to run, then it should run until it exhausts its timeslice.
> >
> > One process looping on sched_yield() and another one doing calculations
> > should result in almost the entire system being devoted to calculations.
> 
> So if you have a database with 20 threads yielding to each other
> each time a lock is contended and one CPU hog the database should
> be reduced to a very small percentage of the CPU ?

If the database threads are at a higher priority than the cpu hog, then no they
shouldn't.  The one that owns the lock should progress as normal.  Assuming that
only the thread owning the lock progresses, the cpu usage ratio between the
threads as a group and the hog should be roughly equivalent to a single database
thread and a single hog.

We certainly shouldn't thrash the yielding threads and starve the hog.

Chris


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