RFR: JDK-8262068: Improve G1 Full GC by skipping compaction for regions with high survival ratio [v14]

[Hamlin Li]

On Wed, 7 Apr 2021 10:33:32 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add sanity check; refine code in update_attribute_table.
>
> src/hotspot/share/gc/g1/g1FullCollector.cpp line 229:
> 
>> 227: 
>> 228: void G1FullCollector::update_attribute_table(HeapRegion* hr) {
>> 229:   if (hr->is_free()) {
> 
> Another item that has been noted in a recent discussion with @albertnetymk is that with this change "Free" regions are also marked as `normal` in the table. It would be better to keep them as "Invalid".
> 
> I.e. something like (incorporating @albertnetymk other suggestion):
> 
>     if (hr->is_free()) {
>       return;
>     } else if (hr->is_closed_archive(...) {
>       [...]
>     } else if (hr->is_pinned() || force_pinned) {
>       [...]
>     } else {
>       [...]
>     }
> 
> There is no real difference as "Free" regions should never be referenced anywhere and the code should assert elsewhere. It's still nice to also have "Free" regions as `Invalid` in that table though.

not exactly. please check previous discussion at https://github.com/openjdk/jdk/pull/2760#discussion_r602144952.

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PR: https://git.openjdk.java.net/jdk/pull/2760