[PATCH 3/7] ntdll: Use CLOCK_REALTIME_COARSE for NtQuerySystemTime() if it has sufficient resolution.

[Huw Davies]

This will only affect users running with HZ=1000.  On an i7-8700 CPU @
3.20GHz it cuts the call cost from ~30ns to ~12ns.

Signed-off-by: Huw Davies 
---
 dlls/ntdll/time.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/dlls/ntdll/time.c b/dlls/ntdll/time.c
index d0a7954377..37401ce2e1 100644
--- a/dlls/ntdll/time.c
+++ b/dlls/ntdll/time.c
@@ -458,19 +458,43 @@ void WINAPI RtlTimeToElapsedTimeFields( const LARGE_INTEGER *Time, PTIME_FIELDS
  * Get the current system time.
  *
  * PARAMS
- *   Time [O] Destination for the current system time.
+ *   time [O] Destination for the current system time.
  *
  * RETURNS
  *   Success: STATUS_SUCCESS.
  *   Failure: An NTSTATUS error code indicating the problem.
  */
-NTSTATUS WINAPI NtQuerySystemTime( PLARGE_INTEGER Time )
+NTSTATUS WINAPI NtQuerySystemTime( LARGE_INTEGER *time )
 {
-    struct timeval now;
+#if defined(HAVE_CLOCK_GETTIME)
+    struct timespec ts;
+    static clockid_t clock_id = -1;

-    gettimeofday( &now, 0 );
-    Time->QuadPart = now.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
-    Time->QuadPart += now.tv_usec * 10;
+    if (clock_id == -1)
+    {
+        struct timespec res;
+
+        /* Use CLOCK_REALTIME_COARSE if it has 1 ms or better resolution */
+        if (!clock_getres( CLOCK_REALTIME_COARSE, &res ) && res.tv_sec == 0 && res.tv_nsec <= 1000000)
+            clock_id = CLOCK_REALTIME_COARSE;
+        else
+            clock_id = CLOCK_REALTIME;
+    }
+
+    if (!clock_gettime( clock_id, &ts ))
+    {
+        time->QuadPart = ts.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
+        time->QuadPart += (ts.tv_nsec + 50) / 100;
+    }
+    else
+#endif
+    {
+        struct timeval now;
+
+        gettimeofday( &now, 0 );
+        time->QuadPart = now.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
+        time->QuadPart += now.tv_usec * 10;
+    }
     return STATUS_SUCCESS;
 }

[Marvin]

Hi,

While running your changed tests, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?

Full results can be found at:
https://testbot.winehq.org/JobDetails.pl?Key=51725

Your paranoid android.

=== debian9 (64 bit WoW report) ===

ntdll:
pipe.c:1557: Test failed: pipe is not signaled
pipe.c:1557: Test failed: pipe is not signaled

[Ken Thomases]

On May 2, 2019, at 3:45 AM, Huw Davies  wrote:
> This will only affect users running with HZ=1000.  On an i7-8700 CPU @
> 3.20GHz it cuts the call cost from ~30ns to ~12ns.
> Signed-off-by: Huw Davies
>
> dlls/ntdll/time.c | 36 ++++++++++++++++++++++++++++++------
> 1 file changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/dlls/ntdll/time.c b/dlls/ntdll/time.c
> index d0a7954377..37401ce2e1 100644
> --- a/dlls/ntdll/time.c
> +++ b/dlls/ntdll/time.c
> @@ -458,19 +458,43 @@ void WINAPI RtlTimeToElapsedTimeFields( const LARGE_INTEGER *Time, PTIME_FIELDS
> - Get the current system time.
> -
> - PARAMS
> -
> - Time [O] Destination for the current system time.
> -
> - time [O] Destination for the current system time.
> -
> - RETURNS
> - Success: STATUS_SUCCESS.
> - Failure: An NTSTATUS error code indicating the problem.
>
> */
> -NTSTATUS WINAPI NtQuerySystemTime( PLARGE_INTEGER Time )
> +NTSTATUS WINAPI NtQuerySystemTime( LARGE_INTEGER *time )
> {
> - struct timeval now;
>
> +#if defined(HAVE_CLOCK_GETTIME)
> - struct timespec ts;
> - static clockid_t clock_id = -1;
> - gettimeofday( &now, 0 );
> - Time->QuadPart = now.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
> - Time->QuadPart += now.tv_usec * 10;
> - if (clock_id == -1)
> - {
> -
>    struct timespec res;
> -
> -
>    /* Use CLOCK_REALTIME_COARSE if it has 1 ms or better resolution */
> -
>    if (!clock_getres( CLOCK_REALTIME_COARSE, &res ) && res.tv_sec == 0 && res.tv_nsec <= 1000000)
> -
>        clock_id = CLOCK_REALTIME_COARSE;
> -
>    else
> -
>        clock_id = CLOCK_REALTIME;

Having clock_gettime() doesn't necessarily imply having CLOCK_REALTIME_COARSE.  It seems that baseline POSIX only requires CLOCK_REALTIME.

-Ken

[Huw Davies]

On Thu, May 02, 2019 at 08:47:29AM -0500, Ken Thomases wrote:
> On May 2, 2019, at 3:45 AM, Huw Davies  wrote:
> > -NTSTATUS WINAPI NtQuerySystemTime( PLARGE_INTEGER Time )
> > +NTSTATUS WINAPI NtQuerySystemTime( LARGE_INTEGER *time )
> > {
> > - struct timeval now;
> >
> > +#if defined(HAVE_CLOCK_GETTIME)
> > - struct timespec ts;
> > - static clockid_t clock_id = -1;
> > - gettimeofday( &now, 0 );
> > - Time->QuadPart = now.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
> > - Time->QuadPart += now.tv_usec * 10;
> > - if (clock_id == -1)
> > - {
> > -
> >    struct timespec res;
> > -
> > -
> >    /* Use CLOCK_REALTIME_COARSE if it has 1 ms or better resolution */
> > -
> >    if (!clock_getres( CLOCK_REALTIME_COARSE, &res ) && res.tv_sec == 0 && res.tv_nsec <= 1000000)
> > -
> >        clock_id = CLOCK_REALTIME_COARSE;
> > -
> >    else
> > -
> >        clock_id = CLOCK_REALTIME;
>
> Having clock_gettime() doesn't necessarily imply having
> CLOCK_REALTIME_COARSE.  It seems that baseline POSIX only requires
> CLOCK_REALTIME.

Good point, thanks!

Huw.