RFR: 8256155: Allow multiple large page sizes to be used on Linux [v30]

[Marcus G K Williams]

On Fri, 30 Apr 2021 07:48:12 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

> Filed [JDK-8266349](https://bugs.openjdk.java.net/browse/JDK-8266349) for passing page size down to `reserve_memory_special`. As I mentioned [here](https://github.com/openjdk/jdk/pull/1153/files#r623353767), if we do this change before this one. We should not have to care about anything but adding the available and configure page sizes to `os::_page_sizes`.

Thanks @kstefanj. Sounds like a clean way to go. Looking forward to seeing the code. Is this likely for JDK17 branch?

> src/hotspot/share/runtime/os.cpp line 1483:
> 
>> 1481:     for (size_t page_size = page_sizes().largest(); page_size != 0;
>> 1482:          page_size = page_sizes().next_smaller(page_size)) {
>> 1483:       if (page_size <= max_page_size && page_size > (size_t)vm_page_size()) {
> 
> Is this really needed?

Probably not. I am doublechecking with some testing.

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PR: https://git.openjdk.java.net/jdk/pull/1153