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

[Walter Bright]

It's in std.file.

Andrei Alexandrescu wrote:
> I think I've seen such a variable elsewhere in Phobos. Walter?
>
> Andrei
>
> On 9/5/10 15:46 CDT, David Simcha wrote:
>> Good point.  I guess maybe a shared static this statement that
>> initializes an immutable variable to either 0 or 1?
>>
>> On 9/5/2010 4:07 PM, Brad Roberts wrote:
>>> 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
>>>>> _______________________________________________
>>>>> phobos mailing list
>>>>> phobos at puremagic.com
>>>>> http://lists.puremagic.com/mailman/listinfo/phobos
>>>>>
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