1.1 --- a/src/os/bsd/vm/os_bsd.cpp Mon May 05 15:10:43 2014 +0200
1.2 +++ b/src/os/bsd/vm/os_bsd.cpp Fri Apr 25 07:40:33 2014 +0200
1.3 @@ -127,8 +127,12 @@
1.4 // global variables
1.5 julong os::Bsd::_physical_memory = 0;
1.6
1.7 -
1.8 +#ifdef __APPLE__
1.9 +mach_timebase_info_data_t os::Bsd::_timebase_info = {0, 0};
1.10 +volatile uint64_t os::Bsd::_max_abstime = 0;
1.11 +#else
1.12 int (*os::Bsd::_clock_gettime)(clockid_t, struct timespec *) = NULL;
1.13 +#endif
1.14 pthread_t os::Bsd::_main_thread;
1.15 int os::Bsd::_page_size = -1;
1.16
1.17 @@ -986,13 +990,15 @@
1.18 return jlong(time.tv_sec) * 1000 + jlong(time.tv_usec / 1000);
1.19 }
1.20
1.21 +#ifndef __APPLE__
1.22 #ifndef CLOCK_MONOTONIC
1.23 #define CLOCK_MONOTONIC (1)
1.24 #endif
1.25 +#endif
1.26
1.27 #ifdef __APPLE__
1.28 void os::Bsd::clock_init() {
1.29 - // XXXDARWIN: Investigate replacement monotonic clock
1.30 + mach_timebase_info(&_timebase_info);
1.31 }
1.32 #else
1.33 void os::Bsd::clock_init() {
1.34 @@ -1007,10 +1013,38 @@
1.35 #endif
1.36
1.37
1.38 +#ifdef __APPLE__
1.39 +
1.40 +jlong os::javaTimeNanos() {
1.41 + const uint64_t tm = mach_absolute_time();
1.42 + const uint64_t now = (tm * Bsd::_timebase_info.numer) / Bsd::_timebase_info.denom;
1.43 + const uint64_t prev = Bsd::_max_abstime;
1.44 + if (now <= prev) {
1.45 + return prev; // same or retrograde time;
1.46 + }
1.47 + const uint64_t obsv = Atomic::cmpxchg(now, (volatile jlong*)&Bsd::_max_abstime, prev);
1.48 + assert(obsv >= prev, "invariant"); // Monotonicity
1.49 + // If the CAS succeeded then we're done and return "now".
1.50 + // If the CAS failed and the observed value "obsv" is >= now then
1.51 + // we should return "obsv". If the CAS failed and now > obsv > prv then
1.52 + // some other thread raced this thread and installed a new value, in which case
1.53 + // we could either (a) retry the entire operation, (b) retry trying to install now
1.54 + // or (c) just return obsv. We use (c). No loop is required although in some cases
1.55 + // we might discard a higher "now" value in deference to a slightly lower but freshly
1.56 + // installed obsv value. That's entirely benign -- it admits no new orderings compared
1.57 + // to (a) or (b) -- and greatly reduces coherence traffic.
1.58 + // We might also condition (c) on the magnitude of the delta between obsv and now.
1.59 + // Avoiding excessive CAS operations to hot RW locations is critical.
1.60 + // See https://blogs.oracle.com/dave/entry/cas_and_cache_trivia_invalidate
1.61 + return (prev == obsv) ? now : obsv;
1.62 +}
1.63 +
1.64 +#else // __APPLE__
1.65 +
1.66 jlong os::javaTimeNanos() {
1.67 if (Bsd::supports_monotonic_clock()) {
1.68 struct timespec tp;
1.69 - int status = Bsd::clock_gettime(CLOCK_MONOTONIC, &tp);
1.70 + int status = Bsd::_clock_gettime(CLOCK_MONOTONIC, &tp);
1.71 assert(status == 0, "gettime error");
1.72 jlong result = jlong(tp.tv_sec) * (1000 * 1000 * 1000) + jlong(tp.tv_nsec);
1.73 return result;
1.74 @@ -1023,6 +1057,8 @@
1.75 }
1.76 }
1.77
1.78 +#endif // __APPLE__
1.79 +
1.80 void os::javaTimeNanos_info(jvmtiTimerInfo *info_ptr) {
1.81 if (Bsd::supports_monotonic_clock()) {
1.82 info_ptr->max_value = ALL_64_BITS;
