RFR: 8253638: Cleanup os::reserve_memory and remove MAP_FIXED

[Stefan Karlsson]

On Fri, 25 Sep 2020 13:18:04 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> src/hotspot/os/linux/os_linux.cpp line 3667:
>> 
>>> 3665: //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
>>> 3666: //  - alignment sets the alignment at which memory shall be allocated.
>>> 3667: //     It must be a multiple of allocation granularity.
>> 
>> (Nothing to do with your patch) but this comment is technically wrong; it should be a multiple of page size. And we
>> probably should assert this in anon_mmap_aligned().
>
> I saw that as well, and I know there are more comments like that in other parts. Maybe we could take a clean-up round
> and fix these.

Created JDK-8253648.

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PR: https://git.openjdk.java.net/jdk/pull/357