RFR: 8271195: Use largest available large page size smaller than LargePageSizeInBytes when available [v3]

[Stefan Johansson]

On Mon, 7 Feb 2022 12:15:03 GMT, Swati Sharma <duke at openjdk.java.net> wrote:

> Are you suggesting that its ok not to honor the alignment which is based on the original large page size?

Hi @swati-sha, 

Not really, we need to make sure the alignment is honored wrt the large page size used (using a larger alignment is still fine though). But I think it would be good to investigate if we could do better during startup if multiple large page sizes are available. I think my example, that a 128m heap is aligned up to 512m if the large page size is 512m, is a case that could be considered a bug, but it is not crystal clear. Cause the user have specified both that it wants large pages but also a heap size of 128m. Which of these are more important? On the other, if we could satisfy the heap of 128m using 2m pages we would be closer to what I would see as the correct solution. This would be achieved today by setting `LargePageSizeInBytes=2m`.

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PR: https://git.openjdk.java.net/jdk/pull/7326