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

[Andrei Alexandrescu]

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
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