RFR: 8305770: os::Linux::available_memory() should refer MemAvailable in /proc/meminfo

[Severin Gehwolf]

On Fri, 5 May 2023 23:27:50 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> We could also just bypass the compiler thread creation question for now. Let the compiler continue to use the old metric when calculating its thread count, but let all other users of os::available_memory() the new one.
>
> @tstuefe @robcasloz 
> 
> I updated this PR to implement both `free_memory` and `available_memory`. In Linux, `free_memory` refers MemFree (equivalent with older `available_memory`), and `available_memory` refers MemAvailable. In other platforms, `free_memory` proxies `available_memory`. And also `CompileBroker` uses `free_memory` rather than `available_memory`. Some GHA checks were failed, but I think they are not caused by this change.

@YaSuenag Windows GHA issue should go away if you merge with latest master. See https://bugs.openjdk.org/browse/JDK-8306543

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PR Comment: https://git.openjdk.org/jdk/pull/13398#issuecomment-1538343451