[PATCH 3/7] ntdll: Use CLOCK_REALTIME_COARSE for NtQuerySystemTime() if it has sufficient resolution.
Huw Davies
huw at codeweavers.com
Thu May 2 03:45:18 CDT 2019
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 <huw at codeweavers.com>
---
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;
}
--
2.17.1
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