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ntdll: Use CLOCK_REALTIME_COARSE for NtQuerySystemTime() if it has sufficient resolution. 

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@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
This commit is contained in:
Huw Davies 2019-05-14 09:53:44 +01:00 committed by Alexandre Julliard
parent 074b7d9d09
commit 5c8ea25014
1 changed files with 32 additions and 6 deletions
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38
dlls/ntdll/time.c
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@ -458,19 +458,45 @@ 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;
#ifdef HAVE_CLOCK_GETTIME
struct timespec ts;
static clockid_t clock_id = CLOCK_MONOTONIC; /* placeholder */
gettimeofday( &now, 0 );
Time->QuadPart = now.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
Time->QuadPart += now.tv_usec * 10;
if (clock_id == CLOCK_MONOTONIC)
{
#ifdef CLOCK_REALTIME_COARSE
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
#endif /* CLOCK_REALTIME_COARSE */
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 /* HAVE_CLOCK_GETTIME */
{
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;
}