RFR: 8321269: Require platforms to define DEFAULT_CACHE_LINE_SIZE

[Stefan Karlsson]

On Mon, 4 Dec 2023 12:42:45 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Found it while doing new code that wants to know the cache line size. Currently, there is a fallback in `globalDefinitions.hpp` that defaults `DEFAULT_CACHE_LINE_SIZE` to `64` if platform does not define it. Instead of relying on default, force platform definitions to tell what is the reasonable default for the platform. This would simplify porting to other architectures, with less surprises for them.
> 
> The actual sizes do not change. If any existing platform needs adjustments, those should be handled as separate issues.

Seems reasonable to me.

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Marked as reviewed by stefank (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16948#pullrequestreview-1762631833