RFR: 8300127: Serial: Remove unnecessary from-space iteration in DefNewGeneration::oop_since_save_marks_iterate [v2]

[Y. Srinivas Ramakrishna]

On Wed, 25 Jan 2023 20:12:04 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Converting no-ops to assertions in young-gen obj iteration.
>> 
>> Test: hotspot_gc
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review

LGTM.

src/hotspot/share/gc/serial/defNewGeneration.inline.hpp line 96:

> 94:   // No allocation in eden and from spaces, so no iteration required.
> 95:   assert(eden()->saved_mark_at_top(), "inv");
> 96:   assert(from()->saved_mark_at_top(), "inv");

Instead of "inv", you could say "No allocation expected in {Eden|From}" (repsectivley).

Glad the assertions were added.

I can't imagine that this would make much of a difference in performance since the calls to eden and from's oop_since_save_marks_iterate would return immediately without doing any work, but I agree it's good to have the assertions as a check against unintended behavior.

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

Marked as reviewed by ysr (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11995