On 5/26/20 12:59 AM, David Holmes wrote:
bug: https://bugs.openjdk.java.net/browse/JDK-8242504
webrev: http://cr.openjdk.java.net/~dholmes/8242504/webrev/
src/hotspot/os/posix/os_posix.hpp
No comments.
src/hotspot/os/posix/os_posix.inline.hpp
No comments.
src/hotspot/os/posix/os_posix.cpp
old L1686: #ifdef NEEDS_LIBRT
old L1687 // Close librt if there is no monotonic clock.
old L1688 if (handle != RTLD_DEFAULT) {
old L1689 dlclose(handle);
old L1690 }
old L1691 #endif
I don't see any explanation in the bug or in the CR invite
about why this code is deleted when this preceding code
remains:
L1658: // For older linux we need librt, for other OS we can find
L1659: // this function in regular libc.
L1660: #ifdef NEEDS_LIBRT
L1661: // We do dlopen's in this particular order due to bug
in linux
L1662: // dynamic loader (see 6348968) leading to crash on exit.
L1663: handle = dlopen("librt.so.1", RTLD_LAZY);
L1664: if (handle == NULL) {
L1665: handle = dlopen("librt.so", RTLD_LAZY);
L1666: }
L1667: #endif
src/hotspot/os/linux/os_linux.cpp
old L1382: return jlong(time.tv_sec) * 1000 + jlong(time.tv_usec
/ 1000);
new L1390: return jlong(time.tv_sec) * MILLIUNITS +
new L1391: jlong(time.tv_usec) / (MICROUNITS / MILLIUNITS);
old L1390: nanos = jlong(time.tv_usec) * 1000;
new L1407: nanos = jlong(time.tv_usec) * (NANOUNITS / MICROUNITS);
Thanks for replacing the literal 1000s in the old code.
test/jdk/java/time/test/java/time/TestClock_System.java
L207: + " millisecond precision:
"+countBetterThanMillisPrecision+"/"+1000);
L209: + " microsecond precision:
"+countBetterThanMicrosPrecision+"/"+1000);
nit - need spaces around some of the '+' operators.
test/micro/org/openjdk/bench/java/lang/SystemTime.java
test/micro/org/openjdk/bench/java/lang/Systems.java
No comments.
My only "concern" is the deletion of closing the librt handle.
If you have a good explanation for that, then I'm good with this patch.
Dan
This work was contributed by Mark Kralj-Taylor:
https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2020-April/038975.html
On the hotspot side we change the Linux implementations of
javaTimeMillis() and javaTimeSystemUTC() so that they use
clock_gettime(CLOCK_REALTIME) instead of gettimeofday(). In keeping
with our conditional use of this API I added a new guard
os::Posix::supports_clock_gettime()
and refined the existing supports_monotonic_clock() so that we can
still use CLOCK_REALTIME if CLOCK_MONOTONIC does not exist. In the
future (hopefully very near future) we will simply assume these APIs
always exist.
On the core-libs side the existing test:
test/jdk/java/time/test/java/time/TestClock_System.java
is adjusted to track the precision in more detail.
Finally Mark has added instantNowAsEpochNanos() to the benchmark
previously known as
test/micro/org/openjdk/bench/java/lang/Systems.java
which I've renamed to SystemTime.java as Mark suggested. I agree
having these three functions measured together makes sense.
Testing:
- test/jdk/java/time/test/java/time/TestClock_System.java
- test/micro/org/openjdk/bench/java/lang/SystemTime.java
- Tiers 1-3
Thanks,
David
