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

[Brad Roberts]

It probably shouldn't be done via a version statement as that's purely a compile
time decisions.  Runtime would allow apps to choose behavior based on where they
run.

On 9/5/2010 11:40 AM, David Simcha wrote:
>  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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> 
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