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Re: Multithreaded Programming : Always use spinlocks for performance?

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On 2022-07-24 at 15:31, Frederick Virchanza Gotham wrote:
> 
> I would post this post to a more generic group like "comp.programming.threads" however it's overrun with spam.
> 
> Earlier this week I posted on "comp.lang.c++" about a class I'd written to get a main thread and 8 worker threads to cooperate with each other.
> 
> I've been doing some testing, and I've tested it 3 ways:
> (1) Using spinlocks
> (2) Using one semaphore, one mutex and one condition_variable
> (3) Using two semaphores per worker thread (i.e. 16 semaphores)
> 
> The slowest is No. 2. I haven't identified the exact reason why yet, but it's about 30 times slower than the other two ways.
> 
> No. 3 is quite good, but not the best.
> 
> No. 1 is the fastest. Is this to be expected? Is the only drawback of using spinlocks that they hog the CPU and so the operating system will be a big laggy?
> 
> So if you don't mind the CPU fan getting a bit load and the OS getting a big laggy, are you best to use spinlocks in your multi-threaded programs?
> 

A spinlock can be good if it is almost always free. It is low cost to 
just test it, and continue without spinning.

A spinlock is really bad if there is a 100 threads spinning on it.


As most of the time with software, there is no simple rule that always 
works. Rather usually "it depends".

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Multithreaded Programming : Always use spinlocks for performance? Frederick Virchanza Gotham <cauldwell.thomas@gmail.com> - 2022-07-24 06:31 -0700
  Re: Multithreaded Programming : Always use spinlocks for performance? Bo Persson <bo@bo-persson.se> - 2022-07-24 15:53 +0200
  Re: Multithreaded Programming : Always use spinlocks for performance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-24 16:42 +0200
  Re: Multithreaded Programming : Always use spinlocks for performance? Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-24 18:09 +0300
    Re: Multithreaded Programming : Always use spinlocks for performance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-24 17:41 +0200
      Re: Multithreaded Programming : Always use spinlocks for performance? Frederick Virchanza Gotham <cauldwell.thomas@gmail.com> - 2022-07-24 09:20 -0700
        Re: Multithreaded Programming : Always use spinlocks for performance? Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-24 19:34 +0300
        Re: Multithreaded Programming : Always use spinlocks for performance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-24 18:57 +0200
        Re: Multithreaded Programming : Always use spinlocks for performance? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-24 11:38 -0700
        Re: Multithreaded Programming : Always use spinlocks for performance? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-07-24 13:17 -0700
          Re: Multithreaded Programming : Always use spinlocks for performance? Öö Tiib <ootiib@hot.ee> - 2022-07-25 03:21 -0700
      Re: Multithreaded Programming : Always use spinlocks for performance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-24 19:01 +0200
  Re: Multithreaded Programming : Always use spinlocks for performance? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-07-24 13:20 -0700
    Re: Multithreaded Programming : Always use spinlocks for performance? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-07-24 16:55 -0700

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