[phobos] Sleep(0) vs Sleep(1) for yield

[David Simcha]

  Seems like a no-brainer to me.  We're basically talking about getting 
rid of workarounds for problems on platforms where the original problem 
doesn't exist.  Thanks for noticing/taking care of this.

On 9/5/2010 12:17 PM, SK wrote:
> Hello,
> Core.thread.yield call has a performance hobbling work-around for
> scheduler problems in Windws XP and earlier:
>
>      /**
>       * Forces a context switch to occur away from the calling thread.
>       */
>      static void yield()
>      {
>          version( Windows )
>          {
>              // NOTE: Sleep(1) is necessary because Sleep(0) does not give
>              //       lower priority threads any timeslice, so looping on
>              //       Sleep(0) could be resource-intensive in some cases.
>              Sleep( 1 );
>          }
>          else version( Posix )
>          {
>              sched_yield();
>          }
>      }
>
>
> Microsoft fortunately fixed the problem for new versions of Windows,
> starting with Windows Server 2003 as described here:
> http://msdn.microsoft.com/en-us/library/ms686298%28VS.85%29.aspx
>
> On Windows 7:
> Sleep(1), the workaround, allows only 1000 thread yields per second
> per core, which is agonizingly slow.
> Sleep(0) allows 4.7 Million yields per second per core on my 2.6GHz machine.
>
> Any objection to changing to Sleep(0) for Windows 2003 and above?
> What definition is suitable for use in version() to make this distinction?
>
> Regards,
> -steve
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