(S) RFR: 8154710: [Solaris] Investigate use of in-memory low-resolution timestamps for Java and internal time API's
david.holmes at oracle.com
Thu Apr 28 23:09:57 UTC 2016
This change is small in nature but somewhat broad in scope. It "affects"
the implementation of System.currentTimeMillis() in the Java space, and
os::javaTimeMillis() in the VM. But on Solaris only.
I say "affects" but the change will be unobservable other than in terms
As of Solaris 11.3.6 a new in-memory timestamp has been made available
(not unlike what has always existed on Windows). There are actually 3
different timestamps exported but the one we are interested in is
get_nsecs_fromepoch - which is of course elapsed nanoseconds since the
epoch - which is exactly what javaTimeMillis() is, but expressed in
milliseconds. The in-memory timestamps have an update accuracy of 1ms,
so are not suitable for any other API's that want the time-of-day, but
at a greater accuracy.
Microbenchmark shows the in-memory access is approx 45% faster (19ns on
my test system) compared to the gettimeofday call (35ns).
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