From 4ac1e9bccbd0222ab779b3fc4d2144d60e1f2b49 Mon Sep 17 00:00:00 2001
From: Auke Kok <sofar@foo-projects.org>
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 | 55 ++++++++++++++++++++++++++++++-------------------
2 files changed, 35 insertions(+), 22 deletions(-)
diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index e7c1b7dd5..7255852e0 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 5da32607c..5fe81a440 100644
--- a/src/porting.h
+++ b/src/porting.h
@@ -211,43 +211,56 @@ void initIrrlicht(irr::IrrlichtDevice * );
}
#else // Posix
-
- inline u32 getTimeS()
+ inline void _os_get_clock(struct timespec *ts)
{
+#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);
+ clock_get_time(cclock, &mts);
+ 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
struct timeval tv;
gettimeofday(&tv, NULL);
- return tv.tv_sec;
+ 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 timeval tv;
- gettimeofday(&tv, NULL);
- return tv.tv_sec * 1000 + tv.tv_usec / 1000;
+ struct timespec ts;
+ _os_get_clock(&ts);
+ return ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
}
inline u32 getTimeUs()
{
- struct timeval tv;
- gettimeofday(&tv, NULL);
- return tv.tv_sec * 1000000 + tv.tv_usec;
+ struct timespec ts;
+ _os_get_clock(&ts);
+ return ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
}
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
- clock_serv_t cclock;
- mach_timespec_t mts;
- host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);
- clock_get_time(cclock, &mts);
- mach_port_deallocate(mach_task_self(), cclock);
- ts.tv_sec = mts.tv_sec;
- ts.tv_nsec = mts.tv_nsec;
-#else
- clock_gettime(CLOCK_REALTIME, &ts);
-#endif
+ _os_get_clock(&ts);
return ts.tv_sec * 1000000000 + ts.tv_nsec;
}
--
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