RFR: 8251158: Implementation of JEP 387: Elastic Metaspace [v11]

[Richard Reingruber]

On Tue, 6 Oct 2020 06:55:40 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> src/hotspot/share/memory/metaspace/binList.hpp line 135:
>> 
>>> 133:         i2++;
>>> 134:         m >>= 1;
>>> 135:       }
>> 
>> I think you overlooked my proposal to make use of `count_trailing_zeros()` instead of this while-loop.
>
> Good point. Lets do this in a follow-up though.

Honestly, without this the optimization is questionable. Iterating the bits in `_mask` is like iterating the list
heads. `is_empty()` can be easily optimized with a counter, but even this is questionable. The change is tiny and easy
to test: just leave the while-loop as an assertion and run some class redefinition tests then remove the loop.

I'd object postponing it.

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PR: https://git.openjdk.java.net/jdk/pull/336