RFR: 8281314: Rename Stack{Red,Yellow,Reserved,Shadow}Pages multipliers to "unit"

[Coleen Phillimore]

On Mon, 7 Feb 2022 07:27:13 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This was a question during [JDK-8072070](https://bugs.openjdk.java.net/browse/JDK-8072070) review. The code in `StackOverflow::initialize_stack_zone_sizes()` multiplies `Stack{Red,Yellow,Reserved,Shadow}Pages` by "alignment", while that is actually just a "unit".
> 
> 
>   product_pd(intx, StackYellowPages, \
>           "Number of yellow zone (recoverable overflows) pages of size " \
>           "4KB. If pages are bigger yellow zone is aligned up.") \
>           range(MIN_STACK_YELLOW_PAGES, (DEFAULT_STACK_YELLOW_PAGES+5)) \
> 
> 
> We can rename it for clarity.

src/hotspot/share/runtime/stackOverflow.cpp line 45:

> 43:   // in 4K pages to the actual os page size. We must do this before setting
> 44:   // up minimal stack sizes etc. in os::init_2().
> 45:   size_t unit = 4*K;

I think we picked 4*k because it was the smallest page size in the platforms that we supported. I might be wrong about that but the name 'unit' should be something else indicative of why it's 4k.

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

PR: https://git.openjdk.java.net/jdk/pull/7362