Use clock_gettime(CLOCK_MONOTONIC) in omrtime_hires_clock #7065
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Recently, gettimeofday was replaced with clock_gettime(CLOCK_MONOTONIC_RAW) in omrtime_hires_clock. This causes a 2-3% regression in startup time. vDSO support for clock_gettime(CLOCK_MONOTONIC_RAW) was added in Linux kernel version 5.3: https://bugzilla.kernel.org/show_bug.cgi?id=198961. The aforementioned regression is seen on Linux kernel versions < 5.3. Replacing CLOCK_MONOTONIC_RAW with CLOCK_MONOTONIC since it has vDSO support for older Linux kernel versions, and it also resolves the above regression in startup time. Related: - eclipse-omr#7041 - eclipse-omr#7044 - https://github.ibm.com/runtimes/javanext/issues/388 - https://github.ibm.com/runtimes/javanext/issues/389 Also, renamed J9TIME_NANO_CLOCK to OMRTIME_NANO_CLOCK. Signed-off-by: Babneet Singh <sbabneet@ca.ibm.com>
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Perf numbers + vDSO support for CLOCK_MONOTONIC_RAW: https://lore.kernel.org/linux-arm-kernel/20190621095252.32307-1-vincenzo.frascino@arm.com. Summary:
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knn-k
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Jul 18, 2023
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Recently, gettimeofday was replaced with
clock_gettime(CLOCK_MONOTONIC_RAW) in omrtime_hires_clock.
This causes a 2-3% regression in startup time.
vDSO support for clock_gettime(CLOCK_MONOTONIC_RAW) was added in Linux
kernel version 5.3: https://bugzilla.kernel.org/show_bug.cgi?id=198961.
The aforementioned regression is seen on Linux kernel versions < 5.3.
Replacing CLOCK_MONOTONIC_RAW with CLOCK_MONOTONIC since it has vDSO
support for older Linux kernel versions, and it also resolves the above
regression in startup time.
Related:
Also, renamed J9TIME_NANO_CLOCK to OMRTIME_NANO_CLOCK.