[Haskell-cafe] Joels Time Leak

Tomasz Zielonka tomasz.zielonka at gmail.com
Thu Dec 29 16:36:37 EST 2005

On Thu, Dec 29, 2005 at 03:34:10PM -0500, Cale Gibbard wrote:
> The issue with it taking too long seems to basically be as Joel said,
> only one of the threads can take that MVar at a time. Even if the time
> that it's taken is fairly short, if one is running faster than the
> others, it tries to take the MVar more often, which means that it runs
> a higher risk of being blocked and slowed down, letting other threads
> take its place. It essentially just forces the scheduler to be more
> fair.

I get results that confirm scheduler unfairness. I have numbered the
threads and every thread prints it number before starting "read".
When there are ORANGE or RED alerts, the output looks odd - below is
the result of "sort -n | uniq -c":

     53 1
     53 2
     21 46
     21 47
      8 109
      8 110
      3 111
      2 998
      2 999
      2 1000

So thread number 1 managed to run at least 52 or 53 "read"s, but thread
number 1000 only 1 or 2 "read"s.

Best regards

I am searching for a programmer who is good at least in some of
[Haskell, ML, C++, Linux, FreeBSD, math] for work in Warsaw, Poland

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