Re: [PATCH 1/2] kernel32: Implement GetSystemTimePreciseAsFileTime

[Andrew Eikum]

On Thu, May 07, 2015 at 11:02:34PM +0300, Martin Storsjo wrote:
> +/***********************************************************************
> -
> -
>          GetSystemTimePreciseAsFileTime  (KERNEL32.@)
> -
> -
> -
> - Get the current time in utc format, with <1 us precision.
> -
> -
> -
> - RETURNS
> -
> - Nothing.
> - */
>
> +VOID WINAPI GetSystemTimePreciseAsFileTime(
> - LPFILETIME time) /* [out] Destination for the current utc time */
>
> +{
> - GetSystemTimeAsFileTime(time);
>
> +}

I don't know why this one's not getting in. I have a couple small
guesses.

Personally, I'm opposed to including a bunch of documentation in Wine.
I don't think Wine is the right place to document the Windows API. I
don't know if others feel this way, or if this is enough for
rejection.

You're also using VOID, LPJUNK, etc, which I think we're trying to
avoid these days.

Andrew

[PATCH 1/2] kernel32: Implement GetSystemTimePreciseAsFileTime

[Martin Storsjö]

On Tue, 12 May 2015, Andrew Eikum wrote:
> On Thu, May 07, 2015 at 11:02:34PM +0300, Martin Storsjo wrote:
> > +/***********************************************************************
> > -
> > -
> >          GetSystemTimePreciseAsFileTime  (KERNEL32.@)
> > -
> > -
> > -
> > - Get the current time in utc format, with <1 us precision.
> > -
> > -
> > -
> > - RETURNS
> > -
> > - Nothing.
> > - */
> >
> > +VOID WINAPI GetSystemTimePreciseAsFileTime(
> > - LPFILETIME time) /* [out] Destination for the current utc time */
> >
> > +{
> > - GetSystemTimeAsFileTime(time);
> >
> > +}
>
> I don't know why this one's not getting in. I have a couple small
> guesses.
>
> Personally, I'm opposed to including a bunch of documentation in Wine.
> I don't think Wine is the right place to document the Windows API. I
> don't know if others feel this way, or if this is enough for
> rejection.
>
> You're also using VOID, LPJUNK, etc, which I think we're trying to
> avoid these days.

Ok, thanks. In this case, it's pretty much a copypaste of the existing 
GetSystemTimeAsFileTime() function, with the body swapped out, and with 
the function comment extended (because to me it's quite puzzling why 
there's two separate functions). Since different parts of the codebase use 
different conventions, I've tried to match the surrounding style unless 
otherwise suggested.

// Martin

[PATCH 1/2] kernel32: Implement GetSystemTimePreciseAsFileTime

[Martin Storsjö]

On Tue, 12 May 2015, Martin Storsjö wrote:
> On Tue, 12 May 2015, Andrew Eikum wrote:
> > On Thu, May 07, 2015 at 11:02:34PM +0300, Martin Storsjo wrote:
> > > +/***********************************************************************
> > > -
> > > -
> > >          GetSystemTimePreciseAsFileTime  (KERNEL32.@)
> > > -
> > > -
> > > -
> > > - Get the current time in utc format, with <1 us precision.
> > > -
> > > -
> > > -
> > > - RETURNS
> > > -
> > > - Nothing.
> > > - */
> > >
> > > +VOID WINAPI GetSystemTimePreciseAsFileTime(
> > > - LPFILETIME time) /* [out] Destination for the current utc time */
> > >
> > > +{
> > > - GetSystemTimeAsFileTime(time);
> > >
> > > +}
> >
> > I don't know why this one's not getting in. I have a couple small
> > guesses.
> >
> > Personally, I'm opposed to including a bunch of documentation in Wine.
> > I don't think Wine is the right place to document the Windows API. I
> > don't know if others feel this way, or if this is enough for
> > rejection.
> >
> > You're also using VOID, LPJUNK, etc, which I think we're trying to
> > avoid these days.
>
> Ok, thanks. In this case, it's pretty much a copypaste of the existing 
> GetSystemTimeAsFileTime() function, with the body swapped out, and with the 
> function comment extended (because to me it's quite puzzling why there's two 
> separate functions).

Alexandre wanted to have tests for this; I did some testing on Windows 8 
(running in a VM). With GetSystemTimeAsFileTime(), the minimum increment I 
get on the returned values is about 15.6 ms, while for 
GetSystemTimePreciseAsFileTime(), I get increments at around 0.3 us, 
possibly even less.

With wine, I get 1 us increments for the existing GetSystemTimeAsFileTime. 
(According to the docs for GetSystemTimePreciseAsFileTime, it should have 
precision < 1 us, but exactly 1 us is probably close enough as well.)

Is there any reason to artifically limit the precision of the current 
function? And does it make sense to have a test that busyloops calling 
both of the functions, finding out the minimum increment of each of the 
functions? By having it run for a couple hundred milliseconds it should 
probably be enough to get useful data, but this still would be a kinda 
brittle test, susceptible to scheduler interruptions.

// Martin

[PATCH 1/2] kernel32: Implement GetSystemTimePreciseAsFileTime

[Alexandre Julliard]

Martin Storsjö  writes:
> Is there any reason to artifically limit the precision of the current
> function? And does it make sense to have a test that busyloops calling
> both of the functions, finding out the minimum increment of each of
> the functions? By having it run for a couple hundred milliseconds it
> should probably be enough to get useful data, but this still would be
> a kinda brittle test, susceptible to scheduler interruptions.

We don't care about the exact precision, so it would be enough to test
that both functions always return the same data within 100ms or so, and
that GetSystemTimePreciseAsFileTime result changes within 1ms or so.