Christian Froeschlin <chr### [at] chrfrde> wrote:
> However, if they do it frequently, one of the threads will always
> be blocked. Using priorities will therefore prevent the situation
> that thread 1 works at 100% and thread2 at 0%, and transform it
> into thread 1 works at 50% and thread2 at 50%.

  Only in a 1-processor/single-core system.

  In a dual-core system the goal is to get as close to 100% and 100% as
possible. If the threads block each other from the resource, you'll get
100% and 0% (on the very extreme), so one of the cores will just sit
idle while the other does all the work.

  (Yes, it's quite unlikely to get to this extreme even with naive
mutexes, but in theory it's still possible. In practice you may still
get reduced efficiency in certain situations, and a FIFO would mostly
solve the problem.)

> An exception would be if thread 1 needs the lock often but
> thread 2 only rarely. But I expect both threads to be doing
> essentially the same task in parallel for speedup, so they
> will also habe the same locking requirements.

  Which is why it's important to distribute the resources to all
threads evenly.

-- 
                                                          - Warp

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