RFR: 8234930: Use MAP_JIT when allocating pages for code cache on macOS

[Anton Kozlov]

On Mon, 28 Sep 2020 11:17:49 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>>> I am sorry, but I dislike the API changes to os::xxx(). As it is now, this API is quite convoluted, undocumented and
>>> inconsistent.
>> 
>> Just to clarify that I did not mean your change makes the API convoluted and inconsistent but that it has been that way
>> already, for a long time. It is a constant headache to get right, especially in ports whose memory management is a bit
>> non-standard, e.g. on AIX.
>
> @tstuefe My patch to remove MAP_FIXED from the memory reservation path should make it possible to revert all the
> os::reserve_memory changes in this patch.

Interesting, thanks! I haven't evaluated the interface, just because it seemed to be out of scope for the task. I'll
take a look and update the patch.

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PR: https://git.openjdk.java.net/jdk/pull/294