RFR: JDK-8305506: Add support for fractional values of SafepointTimeoutDelay [v2]

[David Holmes]

On Mon, 24 Apr 2023 08:01:40 GMT, Wojciech Kudla <duke at openjdk.org> wrote:

>> As stated in https://bugs.openjdk.org/browse/JDK-8305506 this change replaces SafepointTimeoutDelay as integer value with a floating point type to support sub-millisecond SafepointTimeout thresholds.
>> This is immensely useful for investigating time-to-safepoint issues in low latency space.
>
> Wojciech Kudla has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fixed jlong conversion order

Seems fine in principle.

Please add this flag as a testcase for test/hotspot/jtreg/runtime/CommandLine/DoubleFlagWithIntegerValue.java.

Change requested below.

Thanks.

src/hotspot/share/utilities/globalDefinitions.hpp line 170:

> 168: 
> 169: // Format jdouble with defined precision
> 170: #define JDOUBLE_FORMAT_P(precision) "%." #precision "f"

This is not necessary. We only define macros when there are platform differences with format specifiers. Just use `%.6f` directly in the code.

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Changes requested by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13373#pullrequestreview-1403242504
PR Review Comment: https://git.openjdk.org/jdk/pull/13373#discussion_r1178657022