P4
The ShenandoahFreeSet class is shared between Shen and its generational variant aka GenShen.
The following method is called by both ShenandoahHeap's ShenandoahUpdateHeapRefsTask and ShenandoahGenerationalHeap's ShenandoahGenerationalUpdateHeapRefsTask at the start of their respective update refs phases:
```
// Move up to cset_regions number of regions from being available to the collector to being available to the mutator.
//
// Typical usage: At the end of evacuation, when the collector no longer needs the regions that had been reserved
// for evacuation, invoke this to make regions available for mutator allocations.
void move_regions_from_collector_to_mutator(size_t cset_regions);
```
As part of its work, it logs a helpful message:
```
log_info(gc, ergo)("At start of update refs, moving %zu%s to Mutator free set from Collector Reserve ("
"%zu%s) and from Old Collector Reserve (%zu%s)",
byte_size_in_proper_unit(total_xfer), proper_unit_for_byte_size(total_xfer),
byte_size_in_proper_unit(collector_xfer), proper_unit_for_byte_size(collector_xfer),
byte_size_in_proper_unit(old_collector_xfer), proper_unit_for_byte_size(old_collector_xfer));
```
The latter "and from Old Collector Reserve ..." should be elided for the non-generational variant as it can be confusing to a Shenandoah (non-generational) user/log parser.
The following method is called by both ShenandoahHeap's ShenandoahUpdateHeapRefsTask and ShenandoahGenerationalHeap's ShenandoahGenerationalUpdateHeapRefsTask at the start of their respective update refs phases:
```
// Move up to cset_regions number of regions from being available to the collector to being available to the mutator.
//
// Typical usage: At the end of evacuation, when the collector no longer needs the regions that had been reserved
// for evacuation, invoke this to make regions available for mutator allocations.
void move_regions_from_collector_to_mutator(size_t cset_regions);
```
As part of its work, it logs a helpful message:
```
log_info(gc, ergo)("At start of update refs, moving %zu%s to Mutator free set from Collector Reserve ("
"%zu%s) and from Old Collector Reserve (%zu%s)",
byte_size_in_proper_unit(total_xfer), proper_unit_for_byte_size(total_xfer),
byte_size_in_proper_unit(collector_xfer), proper_unit_for_byte_size(collector_xfer),
byte_size_in_proper_unit(old_collector_xfer), proper_unit_for_byte_size(old_collector_xfer));
```
The latter "and from Old Collector Reserve ..." should be elided for the non-generational variant as it can be confusing to a Shenandoah (non-generational) user/log parser.