AuroraMiddleware/qt5base-lts
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Make QElapsedTimer always store nanoseconds in t2

Browse Source 
Up until now, the value stored in t2 depended on whether we had found
a monotonic clock or not. Fix that by always storing nanoseconds: we
avoid extra calculations and accessing a global variable all the time.

The impact is contained to the actual getting of the time. And we
mitigate by using clock_gettime to get the realtime clock instead of
gettimeofday, if that's available.

Change-Id: Iceef2d050fd9472f1a66e11e7ded79fe5163a132
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
This commit is contained in:
Thiago Macieira 2012-08-10 15:00:50 +02:00 committed by Qt by Nokia
parent bc6568291a
commit 46e2c94417
1 changed files with 15 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
src/corelib/tools/qelapsedtimer_unix.cpp
View File

@ -39,6 +39,9 @@
**
****************************************************************************/
// ask for the latest POSIX, just in case
#define _POSIX_C_SOURCE 200809L
#include "qelapsedtimer.h"
#include <sys/time.h>
#include <time.h>
@ -83,18 +86,7 @@ static void unixCheckClockType()
static inline qint64 fractionAdjustment()
{
// disabled, but otherwise indicates bad usage of QElapsedTimer
//Q_ASSERT(monotonicClockChecked);
if (monotonicClockAvailable) {
// the monotonic timer is measured in nanoseconds
// 1 ms = 1000000 ns
return 1000*1000ull;
} else {
// gettimeofday is measured in microseconds
// 1 ms = 1000 us
return 1000;
}
return 1000*1000ull;
}
bool QElapsedTimer::isMonotonic() Q_DECL_NOTHROW
@ -121,11 +113,20 @@ static inline void do_gettime(qint64 *sec, qint64 *frac)
return;
}
#endif
#ifdef CLOCK_REALTIME
// even if we don't have a monotonic clock,
// we can use clock_gettime -> nanosecond resolution
timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
*sec = ts.tv_sec;
*frac = ts.tv_nsec;
#else
// use gettimeofday
timeval tv;
::gettimeofday(&tv, 0);
*sec = tv.tv_sec;
*frac = tv.tv_usec;
*frac = tv.tv_usec * 1000;
#endif
}
// used in qcore_unix.cpp and qeventdispatcher_unix.cpp
@ -136,9 +137,7 @@ timeval qt_gettime() Q_DECL_NOTHROW
timeval tv;
tv.tv_sec = sec;
tv.tv_usec = frac;
if (monotonicClockAvailable)
tv.tv_usec /= 1000;
tv.tv_usec = frac / 1000;
return tv;
}
@ -168,8 +167,6 @@ qint64 QElapsedTimer::nsecsElapsed() const Q_DECL_NOTHROW
do_gettime(&sec, &frac);
sec = sec - t1;
frac = frac - t2;
if (!monotonicClockAvailable)
frac *= 1000;
return sec * Q_INT64_C(1000000000) + frac;
}