[ruby-core:31357] Re: [Bug #3587] windows: unable to sleep < 0.015s

On 19 Jul 2010, at 16:19, KOSAKI Motohiro wrote:

> Hi
> 
> 2010/7/19 Roger Pack <[e-mail]>:
>> Bug #3587: windows: unable to sleep < 0.015s
>> http://redmine.ruby-lang.org/issues/show/3587
>> 
>> Author: Roger Pack
>> Status: Open, Priority: Normal
>> ruby -v: ruby 1.9.3dev (2010-07-19 trunk 28684) [i386-mingw32]
>> 
>>>> sleep 0.0001; Hitimes::Interval.measure { 2.times { sleep 0.000001}}
>> => 0.03124279761813303
>> 
>> (it's always 0.03s)
>> This surprised me a bit, since it differed from Linux behavior.
>> Thanks!
> 
> Typically, windows has 1/64sec (15.625ms) tick resolution. but linux has
> 1/1000sec tick resolution. So, I don't surprised this so much.
> 
> Do you have any improvement idea?

I am told there is a better way to do this (iirc, some media api), but, this is aged code I have for it:

#include "stdafx.h"
#include <Windows.h>
typedef LONG NTSTATUS; 
typedef NTSTATUS (__stdcall *NSTR)(ULONG, BOOLEAN, PULONG); 
#define STATUS_SUCCESS ((NTSTATUS)0x00000000L) 
BOOL NtSetTimerResolution 
( 
        IN ULONG RequestedResolution, 
        IN BOOLEAN Set, 
        OUT PULONG ActualResolution 
);

int _tmain(int argc, _TCHAR* argv[])
{
	HMODULE hNtDll = ::LoadLibrary(_T("ntdll.dll")); 
	BOOL fRetVal = FALSE; 
	ULONG RequestedResolution = 10000, ActualResolution = 0; 
	BOOL Set = true; 
	if (hNtDll) 
	{ 
	  NSTR pNSTR = (NSTR)::GetProcAddress(hNtDll, "NtSetTimerResolution"); 
	  if (pNSTR) 
	  { 
		NTSTATUS nts = (*pNSTR)(RequestedResolution, Set, &ActualResolution); 
		if (STATUS_SUCCESS == nts) 
		  while (true)
			Sleep(100000);
		else
		  return 1;  
	  } 
	}
}

If the API is restricted by timer resolution, this code running as an application on the system should open that up to 1ms, other methods for doing this include running flash or opening media player.

I believe there are ways to do better, but I had another purpose for this code running as a service.

Roger - if this helps, I can provide a patch to hitimes, let me know.