RFR: 8264412: AArch64: CPU description should refer DMI [v2]

[Yasumasa Suenaga]

On Wed, 31 Mar 2021 08:45:06 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Please be more explicit. This is (perhaps obviously?) a workaround for a bug, And t.his code is itself a bug, because it doesn't check for the condition you care about. So, please check explicitly for this condition: `\n` only, and nothing else. And leave a comment explaining why.
>
> One other thing I missed last time around: why is there a permanently-allocated 4k buffer for this code that it only used for jfr?

I pushed new commit with some refactoring.

> Please be more explicit. This is (perhaps obviously?) a workaround for a bug, And t.his code is itself a bug, because it doesn't check for the condition you care about. So, please check explicitly for this condition: \n only, and nothing else. And leave a comment explaining why.

I've done so in new commit.

> One other thing I missed last time around: why is there a permanently-allocated 4k buffer for this code that it only used for jfr?

Some features (e.g. hs_err log, VM.info dcmd) dumps /proc/cpuinfo, so I guess this feature is used JFR only now. However CPU description has different information (for AArch64 at least), so we might be able to use it in other place, but it is out of scope this PR.

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PR: https://git.openjdk.java.net/jdk/pull/3259