--- old/src/hotspot/share/gc/g1/collectionSetChooser.hpp 2019-01-23 10:43:51.913564453 +0100 +++ new/src/hotspot/share/gc/g1/collectionSetChooser.hpp 2019-01-23 10:43:51.423549043 +0100 @@ -26,177 +26,36 @@ #define SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP #include "gc/g1/heapRegion.hpp" -#include "utilities/growableArray.hpp" +#include "memory/allocation.hpp" +#include "runtime/globals.hpp" -class CollectionSetChooser: public CHeapObj { +class G1CollectionSetCandidates; +class WorkGang; - GrowableArray _regions; - - // Unfortunately, GrowableArray uses ints for length and indexes. To - // avoid excessive casting in the rest of the class the following - // wrapper methods are provided that use uints. - - uint regions_length() { return (uint) _regions.length(); } - HeapRegion* regions_at(uint i) { return _regions.at((int) i); } - void regions_at_put(uint i, HeapRegion* hr) { - _regions.at_put((int) i, hr); - } - void regions_at_put_grow(uint i, HeapRegion* hr) { - _regions.at_put_grow((int) i, hr); - } - void regions_trunc_to(uint i) { _regions.trunc_to((uint) i); } - - // The index of the next candidate old region to be considered for - // addition to the CSet. - uint _front; - - // The index of the last candidate old region - uint _end; - - // Keeps track of the start of the next array chunk to be claimed by - // parallel GC workers. - uint _first_par_unreserved_idx; - - // If a region has more live bytes than this threshold, it will not - // be added to the CSet chooser and will not be a candidate for - // collection. - size_t _region_live_threshold_bytes; - - // The sum of reclaimable bytes over all the regions in the CSet chooser. - size_t _remaining_reclaimable_bytes; - - // Calculate and return chunk size (in number of regions) for parallel - // addition of regions - uint calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const; +// Helper class to calculate collection set candidates, and containing some related +// methods. +class CollectionSetChooser : public AllStatic { + static uint calculate_work_chunk_size(uint num_workers, uint num_regions); public: - - // Return the current candidate region to be considered for - // collection without removing it from the CSet chooser. - HeapRegion* peek() { - HeapRegion* res = NULL; - if (_front < _end) { - res = regions_at(_front); - assert(res != NULL, "Unexpected NULL hr in _regions at index %u", _front); - } - return res; - } - - // Remove the given region from the CSet chooser and move to the - // next one. - HeapRegion* pop() { - HeapRegion* hr = regions_at(_front); - assert(hr != NULL, "pre-condition"); - assert(_front < _end, "pre-condition"); - regions_at_put(_front, NULL); - assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes, - "remaining reclaimable bytes inconsistent " - "from region: " SIZE_FORMAT " remaining: " SIZE_FORMAT, - hr->reclaimable_bytes(), _remaining_reclaimable_bytes); - _remaining_reclaimable_bytes -= hr->reclaimable_bytes(); - _front += 1; - return hr; - } - - void push(HeapRegion* hr); - CollectionSetChooser(); static size_t mixed_gc_live_threshold_bytes() { return HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100; } - static bool region_occupancy_low_enough_for_evac(size_t live_bytes); - - void sort_regions(); + static bool region_occupancy_low_enough_for_evac(size_t live_bytes) { + return live_bytes < mixed_gc_live_threshold_bytes(); + } - // Determine whether to add the given region to the CSet chooser or + // Determine whether to add the given region to the collection set candidates or // not. Currently, we skip pinned regions and regions whose live // bytes are over the threshold. Humongous regions may be reclaimed during cleanup. // Regions also need a complete remembered set to be a candidate. - bool should_add(HeapRegion* hr) const; - - // Returns the number candidate old regions added - uint length() { return _end; } - - // Serial version. - void add_region(HeapRegion *hr); - - // Must be called before calls to claim_array_chunk(). - // n_regions is the number of regions, chunk_size the chunk size. - void prepare_for_par_region_addition(uint n_threads, uint n_regions, uint chunk_size); - // Returns the first index in a contiguous chunk of chunk_size indexes - // that the calling thread has reserved. These must be set by the - // calling thread using set_region() (to NULL if necessary). - uint claim_array_chunk(uint chunk_size); - // Set the marked array entry at index to hr. Careful to claim the index - // first if in parallel. - void set_region(uint index, HeapRegion* hr); - // Atomically increment the number of added regions by region_num - // and the amount of reclaimable bytes by reclaimable_bytes. - void update_totals(uint region_num, size_t reclaimable_bytes); - - // Iterate over all collection set candidate regions. - void iterate(HeapRegionClosure* cl); - - void clear(); - - void rebuild(WorkGang* workers, uint n_regions); - - // Return the number of candidate regions that remain to be collected. - uint remaining_regions() { return _end - _front; } - - // Determine whether the CSet chooser has more candidate regions or not. - bool is_empty() { return remaining_regions() == 0; } - - // Return the reclaimable bytes that remain to be collected on - // all the candidate regions in the CSet chooser. - size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; } - - // Returns true if the used portion of "_regions" is properly - // sorted, otherwise asserts false. - void verify() PRODUCT_RETURN; -}; - -class CSetChooserParUpdater : public StackObj { -private: - CollectionSetChooser* _chooser; - bool _parallel; - uint _chunk_size; - uint _cur_chunk_idx; - uint _cur_chunk_end; - uint _regions_added; - size_t _reclaimable_bytes_added; - -public: - CSetChooserParUpdater(CollectionSetChooser* chooser, - bool parallel, uint chunk_size) : - _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size), - _cur_chunk_idx(0), _cur_chunk_end(0), - _regions_added(0), _reclaimable_bytes_added(0) { } - - ~CSetChooserParUpdater() { - if (_parallel && _regions_added > 0) { - _chooser->update_totals(_regions_added, _reclaimable_bytes_added); - } - } - - void add_region(HeapRegion* hr) { - if (_parallel) { - if (_cur_chunk_idx == _cur_chunk_end) { - _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size); - _cur_chunk_end = _cur_chunk_idx + _chunk_size; - } - assert(_cur_chunk_idx < _cur_chunk_end, "invariant"); - _chooser->set_region(_cur_chunk_idx, hr); - _cur_chunk_idx += 1; - } else { - _chooser->add_region(hr); - } - _regions_added += 1; - _reclaimable_bytes_added += hr->reclaimable_bytes(); - } + static bool should_add(HeapRegion* hr); - bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); } + // Build and return set of collection set candidates sorted by decreasing gc + // efficiency. + static G1CollectionSetCandidates* build(WorkGang* workers, uint max_num_regions); }; #endif // SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP