RFR: 8273872: ZGC: Explicitly use 2M large pages

[Erik Österlund]

On Thu, 16 Sep 2021 07:59:32 GMT, Per Liden <pliden at openjdk.org> wrote:

> ZGC requires large pages to be 2M. However, ZGC doesn't explicitly asks for this page size and instead relies on the default large pages size for the system to be 2M. On systems where this is not true, ZGC will fails with an error message. To avoid this, ZGC should explicitly ask for 2M large pages and not rely on the system default. Furthermore, ZGC currently ignores `-XX:LargePageSizeInBytes`. ZGC should fails with an error message if it's specified to something other than 2M.

Actually it looks like LargePageSizeInBytes is wrong if not set explicitly to 2M, so it ends up bailing out even though the user didn't specify any particular size.

-------------

Changes requested by eosterlund (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5541