RFR: 8324817: Parallel GC does not pre-touch all heap pages when AlwaysPreTouch enabled and large page disabled

[Albert Mingkun Yang]

On Mon, 29 Jan 2024 08:34:37 GMT, Wang Zhuo <wzhuo at openjdk.org> wrote:

> On linux we can reproduce this bug when /sys/kernel/mm/transparent_hugepage/enabled is madvise or never, but cannot reproduce when it is always.

Could you explain why this bug is affected by that OS config flag? As you pointed out, `alignment()` (is `GenAlignment` as I read the code) can be different from `os::vm_page_size()`, so pretouching uses the wrong page-size. However, I don't get how `transparent_hugepage` is related here.

A semi-related issue, if `alignment()` can have the wrong page-size, does it mean `numa_setup_pages` (a few lines above) also needs revision?

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PR Comment: https://git.openjdk.org/jdk/pull/17610#issuecomment-1914672302