From 4ac1e9bccbd0222ab779b3fc4d2144d60e1f2b49 Mon Sep 17 00:00:00 2001 From: Auke Kok Date: Sat, 23 Jan 2016 23:06:26 -0800 Subject: [PATCH] Clocksource: use a better clock if available. clock_gettime() is a far better clock than gettimeofday(). Even better than clock_gettime() is that you can select either CLOCK_MONOTONIC, or even CLOCK_MONOTONIC_RAW. These clocks offer high precision time. And the _RAW variant will never roll back due to NTP drift or daylight savings, or otherwise. I've adjusted this code to select the right clock method auto- matically based on what's available in the OS. This means that if you're running a very old linux version, MacOS or other, you will automatically get the best clocksource available. I've tested all Linux clocksources by selectively compiling and running a 10k+ timer test suite. In all cases I confirmed that the 3 POSIX Linux clocksources worked properly, and were selected properly. I've modified the OS X compile path to use the high-res clock source for all time functions, but I can't confirm it works or that it compiles. As for WIN32, I confirmed that the used clocksource is indeed a Monotonic clocksource, so good news: that code section appears to be exactly what it should be. --- doc/lua_api.txt | 2 +- src/porting.h | 69 +++++++++++++++++++++++++++++-------------------- 2 files changed, 42 insertions(+), 29 deletions(-) diff --git a/doc/lua_api.txt b/doc/lua_api.txt index e7c1b7dd..7255852e 100644 --- a/doc/lua_api.txt +++ b/doc/lua_api.txt @@ -1727,7 +1727,7 @@ Helper functions * `minetest.is_yes(arg)` * returns whether `arg` can be interpreted as yes * `minetest.get_us_time()` - * returns time with microsecond precision + * returns time with microsecond precision. May not return wall time. * `table.copy(table)`: returns a table * returns a deep copy of `table` diff --git a/src/porting.h b/src/porting.h index 5da32607..5fe81a44 100644 --- a/src/porting.h +++ b/src/porting.h @@ -211,33 +211,11 @@ void initIrrlicht(irr::IrrlichtDevice * ); } #else // Posix - - inline u32 getTimeS() + inline void _os_get_clock(struct timespec *ts) { - struct timeval tv; - gettimeofday(&tv, NULL); - return tv.tv_sec; - } - - inline u32 getTimeMs() - { - struct timeval tv; - gettimeofday(&tv, NULL); - return tv.tv_sec * 1000 + tv.tv_usec / 1000; - } - - inline u32 getTimeUs() - { - struct timeval tv; - gettimeofday(&tv, NULL); - return tv.tv_sec * 1000000 + tv.tv_usec; - } - - inline u32 getTimeNs() - { - struct timespec ts; - // from http://stackoverflow.com/questions/5167269/clock-gettime-alternative-in-mac-os-x -#if defined(__MACH__) && defined(__APPLE__) // OS X does not have clock_gettime, use clock_get_time +#if defined(__MACH__) && defined(__APPLE__) + // from http://stackoverflow.com/questions/5167269/clock-gettime-alternative-in-mac-os-x + // OS X does not have clock_gettime, use clock_get_time clock_serv_t cclock; mach_timespec_t mts; host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock); @@ -245,9 +223,44 @@ void initIrrlicht(irr::IrrlichtDevice * ); mach_port_deallocate(mach_task_self(), cclock); ts.tv_sec = mts.tv_sec; ts.tv_nsec = mts.tv_nsec; +#elif defined(CLOCK_MONOTONIC_RAW) + clock_gettime(CLOCK_MONOTONIC_RAW, ts); +#elif defined(_POSIX_MONOTONIC_CLOCK) + clock_gettime(CLOCK_MONOTONIC, ts); #else - clock_gettime(CLOCK_REALTIME, &ts); -#endif + struct timeval tv; + gettimeofday(&tv, NULL); + TIMEVAL_TO_TIMESPEC(&tv, ts); +#endif // defined(__MACH__) && defined(__APPLE__) + } + + // Note: these clock functions do not return wall time, but + // generally a clock that starts at 0 when the process starts. + inline u32 getTimeS() + { + struct timespec ts; + _os_get_clock(&ts); + return ts.tv_sec; + } + + inline u32 getTimeMs() + { + struct timespec ts; + _os_get_clock(&ts); + return ts.tv_sec * 1000 + ts.tv_nsec / 1000000; + } + + inline u32 getTimeUs() + { + struct timespec ts; + _os_get_clock(&ts); + return ts.tv_sec * 1000000 + ts.tv_nsec / 1000; + } + + inline u32 getTimeNs() + { + struct timespec ts; + _os_get_clock(&ts); return ts.tv_sec * 1000000000 + ts.tv_nsec; }