src/share/vm/memory/genCollectedHeap.cpp

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rev 2870 : 7117303: VM uses non-monotonic time source and complains that it is non-monotonic
Summary: Replaces calls to os::javaTimeMillis(), which does not guarantee montonicity, in GC code to os::javaTimeNanos() with a suitable conversion factor. os::javaTimeNanos is guaranteed monotonic if the underlying platform provides a monotonic timesource. Changes in OS files are to make use of the newly defined constants in globalDefinitions.hpp.
Reviewed-by: dholmes

*** 1458,1486 **** _time = MIN2(_time, gen->time_of_last_gc(_now)); } }; jlong GenCollectedHeap::millis_since_last_gc() { ! jlong now = os::javaTimeMillis(); GenTimeOfLastGCClosure tolgc_cl(now); // iterate over generations getting the oldest // time that a generation was collected generation_iterate(&tolgc_cl, false); tolgc_cl.do_generation(perm_gen()); ! // XXX Despite the assert above, since javaTimeMillis() ! // doesnot guarantee monotonically increasing return ! // values (note, i didn't say "strictly monotonic"), ! // we need to guard against getting back a time ! // later than now. This should be fixed by basing ! // on someting like gethrtime() which guarantees ! // monotonicity. Note that cond_wait() is susceptible ! // to a similar problem, because its interface is ! // based on absolute time in the form of the ! // system time's notion of UCT. See also 4506635 ! // for yet another problem of similar nature. XXX jlong retVal = now - tolgc_cl.time(); if (retVal < 0) { ! NOT_PRODUCT(warning("time warp: %d", retVal);) return 0; } return retVal; } --- 1458,1482 ---- _time = MIN2(_time, gen->time_of_last_gc(_now)); } }; jlong GenCollectedHeap::millis_since_last_gc() { ! // We need a montonically increasing time in ms but os::javaTimeMillis() ! // does not guarantee montonicity. ! jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; GenTimeOfLastGCClosure tolgc_cl(now); // iterate over generations getting the oldest // time that a generation was collected generation_iterate(&tolgc_cl, false); tolgc_cl.do_generation(perm_gen()); ! ! // javaTimeNanos() is guaranteed to be monotonically non-decreasing ! // provided the underlying platform provides such a time source ! // (and it is bug free). So we still have to guard against getting ! // back a time later than 'now'. jlong retVal = now - tolgc_cl.time(); if (retVal < 0) { ! NOT_PRODUCT(warning("time warp: "INT64_FORMAT, retVal);) return 0; } return retVal; }