RFR: 8333236: Test java/foreign/TestAccessModes.java is timing out after passing [v2]

[Maurizio Cimadamore]

On Fri, 31 May 2024 16:15:12 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This PR restores a var handle cache in `Utils::makeSegmentViewVarHandle`. The cache was moved to `ValueLayouts::varHandle` as part of [pull/19251](https://git.openjdk.org/jdk/pull/19251), on the basis that we want to optimize the common case like:
>> 
>> 
>> ValueLayout layout = ...
>> layout.varHandle().get(...)
>> 
>> 
>> And that caching more complex var handles didn't seem to add value, given that, for these var handles, the logic in `LayoutPath` needs to adapt the returned var handle anyways.
>> 
>> But, `TestAccessModes` revealed a different picture - w/o any cache in `Utils` the test end up allocating 8963 var handle instances (instead of just 4), in each of the 4 runs the test includes. While this is admittedly a stress test, it seems nice to restore the level of sharing we had before [pull/19251](https://git.openjdk.org/jdk/pull/19251).
>
> Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address review comments

src/java.base/share/classes/jdk/internal/foreign/Utils.java line 106:

> 104:      * @return a raw memory segment var handle.
> 105:      */
> 106:     public static VarHandle makeRawSegmentViewVarHandle(ValueLayout layout) {

Since I was here, I took the opportunity to rename this to include `raw`, to denote that the var handle returned by this method should not be exposed by APIs as is.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19485#discussion_r1622666280