/* * Copyright (c) 2005, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_VM_GC_PARALLEL_PSPARALLELCOMPACT_HPP #define SHARE_VM_GC_PARALLEL_PSPARALLELCOMPACT_HPP #include "gc/parallel/mutableSpace.hpp" #include "gc/parallel/objectStartArray.hpp" #include "gc/parallel/parMarkBitMap.hpp" #include "gc/parallel/parallelScavengeHeap.hpp" #include "gc/shared/collectedHeap.hpp" #include "gc/shared/collectorCounters.hpp" #include "oops/oop.hpp" class ParallelScavengeHeap; class PSAdaptiveSizePolicy; class PSYoungGen; class PSOldGen; class ParCompactionManager; class ParallelTaskTerminator; class PSParallelCompact; class GCTaskManager; class GCTaskQueue; class PreGCValues; class MoveAndUpdateClosure; class RefProcTaskExecutor; class ParallelOldTracer; class STWGCTimer; // The SplitInfo class holds the information needed to 'split' a source region // so that the live data can be copied to two destination *spaces*. Normally, // all the live data in a region is copied to a single destination space (e.g., // everything live in a region in eden is copied entirely into the old gen). // However, when the heap is nearly full, all the live data in eden may not fit // into the old gen. Copying only some of the regions from eden to old gen // requires finding a region that does not contain a partial object (i.e., no // live object crosses the region boundary) somewhere near the last object that // does fit into the old gen. Since it's not always possible to find such a // region, splitting is necessary for predictable behavior. // // A region is always split at the end of the partial object. This avoids // additional tests when calculating the new location of a pointer, which is a // very hot code path. The partial object and everything to its left will be // copied to another space (call it dest_space_1). The live data to the right // of the partial object will be copied either within the space itself, or to a // different destination space (distinct from dest_space_1). // // Split points are identified during the summary phase, when region // destinations are computed: data about the split, including the // partial_object_size, is recorded in a SplitInfo record and the // partial_object_size field in the summary data is set to zero. The zeroing is // possible (and necessary) since the partial object will move to a different // destination space than anything to its right, thus the partial object should // not affect the locations of any objects to its right. // // The recorded data is used during the compaction phase, but only rarely: when // the partial object on the split region will be copied across a destination // region boundary. This test is made once each time a region is filled, and is // a simple address comparison, so the overhead is negligible (see // PSParallelCompact::first_src_addr()). // // Notes: // // Only regions with partial objects are split; a region without a partial // object does not need any extra bookkeeping. // // At most one region is split per space, so the amount of data required is // constant. // // A region is split only when the destination space would overflow. Once that // happens, the destination space is abandoned and no other data (even from // other source spaces) is targeted to that destination space. Abandoning the // destination space may leave a somewhat large unused area at the end, if a // large object caused the overflow. // // Future work: // // More bookkeeping would be required to continue to use the destination space. // The most general solution would allow data from regions in two different // source spaces to be "joined" in a single destination region. At the very // least, additional code would be required in next_src_region() to detect the // join and skip to an out-of-order source region. If the join region was also // the last destination region to which a split region was copied (the most // likely case), then additional work would be needed to get fill_region() to // stop iteration and switch to a new source region at the right point. Basic // idea would be to use a fake value for the top of the source space. It is // doable, if a bit tricky. // // A simpler (but less general) solution would fill the remainder of the // destination region with a dummy object and continue filling the next // destination region. class SplitInfo { public: // Return true if this split info is valid (i.e., if a split has been // recorded). The very first region cannot have a partial object and thus is // never split, so 0 is the 'invalid' value. bool is_valid() const { return _src_region_idx > 0; } // Return true if this split holds data for the specified source region. inline bool is_split(size_t source_region) const; // The index of the split region, the size of the partial object on that // region and the destination of the partial object. size_t src_region_idx() const { return _src_region_idx; } size_t partial_obj_size() const { return _partial_obj_size; } HeapWord* destination() const { return _destination; } // The destination count of the partial object referenced by this split // (either 1 or 2). This must be added to the destination count of the // remainder of the source region. unsigned int destination_count() const { return _destination_count; } // If a word within the partial object will be written to the first word of a // destination region, this is the address of the destination region; // otherwise this is NULL. HeapWord* dest_region_addr() const { return _dest_region_addr; } // If a word within the partial object will be written to the first word of a // destination region, this is the address of that word within the partial // object; otherwise this is NULL. HeapWord* first_src_addr() const { return _first_src_addr; } // Record the data necessary to split the region src_region_idx. void record(size_t src_region_idx, size_t partial_obj_size, HeapWord* destination); void clear(); DEBUG_ONLY(void verify_clear();) private: size_t _src_region_idx; size_t _partial_obj_size; HeapWord* _destination; unsigned int _destination_count; HeapWord* _dest_region_addr; HeapWord* _first_src_addr; }; inline bool SplitInfo::is_split(size_t region_idx) const { return _src_region_idx == region_idx && is_valid(); } class SpaceInfo { public: MutableSpace* space() const { return _space; } // Where the free space will start after the collection. Valid only after the // summary phase completes. HeapWord* new_top() const { return _new_top; } // Allows new_top to be set. HeapWord** new_top_addr() { return &_new_top; } // Where the smallest allowable dense prefix ends (used only for perm gen). HeapWord* min_dense_prefix() const { return _min_dense_prefix; } // Where the dense prefix ends, or the compacted region begins. HeapWord* dense_prefix() const { return _dense_prefix; } // The start array for the (generation containing the) space, or NULL if there // is no start array. ObjectStartArray* start_array() const { return _start_array; } SplitInfo& split_info() { return _split_info; } void set_space(MutableSpace* s) { _space = s; } void set_new_top(HeapWord* addr) { _new_top = addr; } void set_min_dense_prefix(HeapWord* addr) { _min_dense_prefix = addr; } void set_dense_prefix(HeapWord* addr) { _dense_prefix = addr; } void set_start_array(ObjectStartArray* s) { _start_array = s; } void publish_new_top() const { _space->set_top(_new_top); } private: MutableSpace* _space; HeapWord* _new_top; HeapWord* _min_dense_prefix; HeapWord* _dense_prefix; ObjectStartArray* _start_array; SplitInfo _split_info; }; class ParallelCompactData { public: // Sizes are in HeapWords, unless indicated otherwise. static const size_t Log2RegionSize; static const size_t RegionSize; static const size_t RegionSizeBytes; // Mask for the bits in a size_t to get an offset within a region. static const size_t RegionSizeOffsetMask; // Mask for the bits in a pointer to get an offset within a region. static const size_t RegionAddrOffsetMask; // Mask for the bits in a pointer to get the address of the start of a region. static const size_t RegionAddrMask; static const size_t Log2BlockSize; static const size_t BlockSize; static const size_t BlockSizeBytes; static const size_t BlockSizeOffsetMask; static const size_t BlockAddrOffsetMask; static const size_t BlockAddrMask; static const size_t BlocksPerRegion; static const size_t Log2BlocksPerRegion; class RegionData { public: // Destination address of the region. HeapWord* destination() const { return _destination; } // The first region containing data destined for this region. size_t source_region() const { return _source_region; } // The object (if any) starting in this region and ending in a different // region that could not be updated during the main (parallel) compaction // phase. This is different from _partial_obj_addr, which is an object that // extends onto a source region. However, the two uses do not overlap in // time, so the same field is used to save space. HeapWord* deferred_obj_addr() const { return _partial_obj_addr; } // The starting address of the partial object extending onto the region. HeapWord* partial_obj_addr() const { return _partial_obj_addr; } // Size of the partial object extending onto the region (words). size_t partial_obj_size() const { return _partial_obj_size; } // Size of live data that lies within this region due to objects that start // in this region (words). This does not include the partial object // extending onto the region (if any), or the part of an object that extends // onto the next region (if any). size_t live_obj_size() const { return _dc_and_los & los_mask; } // Total live data that lies within the region (words). size_t data_size() const { return partial_obj_size() + live_obj_size(); } // The destination_count is the number of other regions to which data from // this region will be copied. At the end of the summary phase, the valid // values of destination_count are // // 0 - data from the region will be compacted completely into itself, or the // region is empty. The region can be claimed and then filled. // 1 - data from the region will be compacted into 1 other region; some // data from the region may also be compacted into the region itself. // 2 - data from the region will be copied to 2 other regions. // // During compaction as regions are emptied, the destination_count is // decremented (atomically) and when it reaches 0, it can be claimed and // then filled. // // A region is claimed for processing by atomically changing the // destination_count to the claimed value (dc_claimed). After a region has // been filled, the destination_count should be set to the completed value // (dc_completed). inline uint destination_count() const; inline uint destination_count_raw() const; // Whether the block table for this region has been filled. inline bool blocks_filled() const; // Number of times the block table was filled. DEBUG_ONLY(inline size_t blocks_filled_count() const;) // The location of the java heap data that corresponds to this region. inline HeapWord* data_location() const; // The highest address referenced by objects in this region. inline HeapWord* highest_ref() const; // Whether this region is available to be claimed, has been claimed, or has // been completed. // // Minor subtlety: claimed() returns true if the region is marked // completed(), which is desirable since a region must be claimed before it // can be completed. bool available() const { return _dc_and_los < dc_one; } bool claimed() const { return _dc_and_los >= dc_claimed; } bool completed() const { return _dc_and_los >= dc_completed; } // These are not atomic. void set_destination(HeapWord* addr) { _destination = addr; } void set_source_region(size_t region) { _source_region = region; } void set_deferred_obj_addr(HeapWord* addr) { _partial_obj_addr = addr; } void set_partial_obj_addr(HeapWord* addr) { _partial_obj_addr = addr; } void set_partial_obj_size(size_t words) { _partial_obj_size = (region_sz_t) words; } inline void set_blocks_filled(); inline void set_destination_count(uint count); inline void set_live_obj_size(size_t words); inline void set_data_location(HeapWord* addr); inline void set_completed(); inline bool claim_unsafe(); // These are atomic. inline void add_live_obj(size_t words); inline void set_highest_ref(HeapWord* addr); inline void decrement_destination_count(); inline bool claim(); private: // The type used to represent object sizes within a region. typedef uint region_sz_t; // Constants for manipulating the _dc_and_los field, which holds both the // destination count and live obj size. The live obj size lives at the // least significant end so no masking is necessary when adding. static const region_sz_t dc_shift; // Shift amount. static const region_sz_t dc_mask; // Mask for destination count. static const region_sz_t dc_one; // 1, shifted appropriately. static const region_sz_t dc_claimed; // Region has been claimed. static const region_sz_t dc_completed; // Region has been completed. static const region_sz_t los_mask; // Mask for live obj size. HeapWord* _destination; size_t _source_region; HeapWord* _partial_obj_addr; region_sz_t _partial_obj_size; region_sz_t volatile _dc_and_los; bool volatile _blocks_filled; #ifdef ASSERT size_t _blocks_filled_count; // Number of block table fills. // These enable optimizations that are only partially implemented. Use // debug builds to prevent the code fragments from breaking. HeapWord* _data_location; HeapWord* _highest_ref; #endif // #ifdef ASSERT #ifdef ASSERT public: uint _pushed; // 0 until region is pushed onto a stack private: #endif }; // "Blocks" allow shorter sections of the bitmap to be searched. Each Block // holds an offset, which is the amount of live data in the Region to the left // of the first live object that starts in the Block. class BlockData { public: typedef unsigned short int blk_ofs_t; blk_ofs_t offset() const { return _offset; } void set_offset(size_t val) { _offset = (blk_ofs_t)val; } private: blk_ofs_t _offset; }; public: ParallelCompactData(); bool initialize(MemRegion covered_region); size_t region_count() const { return _region_count; } size_t reserved_byte_size() const { return _reserved_byte_size; } // Convert region indices to/from RegionData pointers. inline RegionData* region(size_t region_idx) const; inline size_t region(const RegionData* const region_ptr) const; size_t block_count() const { return _block_count; } inline BlockData* block(size_t block_idx) const; inline size_t block(const BlockData* block_ptr) const; void add_obj(HeapWord* addr, size_t len); void add_obj(oop p, size_t len) { add_obj((HeapWord*)p, len); } // Fill in the regions covering [beg, end) so that no data moves; i.e., the // destination of region n is simply the start of region n. The argument beg // must be region-aligned; end need not be. void summarize_dense_prefix(HeapWord* beg, HeapWord* end); HeapWord* summarize_split_space(size_t src_region, SplitInfo& split_info, HeapWord* destination, HeapWord* target_end, HeapWord** target_next); bool summarize(SplitInfo& split_info, HeapWord* source_beg, HeapWord* source_end, HeapWord** source_next, HeapWord* target_beg, HeapWord* target_end, HeapWord** target_next); void clear(); void clear_range(size_t beg_region, size_t end_region); void clear_range(HeapWord* beg, HeapWord* end) { clear_range(addr_to_region_idx(beg), addr_to_region_idx(end)); } // Return the number of words between addr and the start of the region // containing addr. inline size_t region_offset(const HeapWord* addr) const; // Convert addresses to/from a region index or region pointer. inline size_t addr_to_region_idx(const HeapWord* addr) const; inline RegionData* addr_to_region_ptr(const HeapWord* addr) const; inline HeapWord* region_to_addr(size_t region) const; inline HeapWord* region_to_addr(size_t region, size_t offset) const; inline HeapWord* region_to_addr(const RegionData* region) const; inline HeapWord* region_align_down(HeapWord* addr) const; inline HeapWord* region_align_up(HeapWord* addr) const; inline bool is_region_aligned(HeapWord* addr) const; // Analogous to region_offset() for blocks. size_t block_offset(const HeapWord* addr) const; size_t addr_to_block_idx(const HeapWord* addr) const; size_t addr_to_block_idx(const oop obj) const { return addr_to_block_idx((HeapWord*) obj); } inline BlockData* addr_to_block_ptr(const HeapWord* addr) const; inline HeapWord* block_to_addr(size_t block) const; inline size_t region_to_block_idx(size_t region) const; inline HeapWord* block_align_down(HeapWord* addr) const; inline HeapWord* block_align_up(HeapWord* addr) const; inline bool is_block_aligned(HeapWord* addr) const; // Return the address one past the end of the partial object. HeapWord* partial_obj_end(size_t region_idx) const; // Return the location of the object after compaction. HeapWord* calc_new_pointer(HeapWord* addr, ParCompactionManager* cm); HeapWord* calc_new_pointer(oop p, ParCompactionManager* cm) { return calc_new_pointer((HeapWord*) p, cm); } #ifdef ASSERT void verify_clear(const PSVirtualSpace* vspace); void verify_clear(); #endif // #ifdef ASSERT private: bool initialize_block_data(); bool initialize_region_data(size_t region_size); PSVirtualSpace* create_vspace(size_t count, size_t element_size); private: HeapWord* _region_start; #ifdef ASSERT HeapWord* _region_end; #endif // #ifdef ASSERT PSVirtualSpace* _region_vspace; size_t _reserved_byte_size; RegionData* _region_data; size_t _region_count; PSVirtualSpace* _block_vspace; BlockData* _block_data; size_t _block_count; }; inline uint ParallelCompactData::RegionData::destination_count_raw() const { return _dc_and_los & dc_mask; } inline uint ParallelCompactData::RegionData::destination_count() const { return destination_count_raw() >> dc_shift; } inline bool ParallelCompactData::RegionData::blocks_filled() const { bool result = _blocks_filled; OrderAccess::acquire(); return result; } #ifdef ASSERT inline size_t ParallelCompactData::RegionData::blocks_filled_count() const { return _blocks_filled_count; } #endif // #ifdef ASSERT inline void ParallelCompactData::RegionData::set_blocks_filled() { OrderAccess::release(); _blocks_filled = true; // Debug builds count the number of times the table was filled. DEBUG_ONLY(Atomic::inc(&_blocks_filled_count)); } inline void ParallelCompactData::RegionData::set_destination_count(uint count) { assert(count <= (dc_completed >> dc_shift), "count too large"); const region_sz_t live_sz = (region_sz_t) live_obj_size(); _dc_and_los = (count << dc_shift) | live_sz; } inline void ParallelCompactData::RegionData::set_live_obj_size(size_t words) { assert(words <= los_mask, "would overflow"); _dc_and_los = destination_count_raw() | (region_sz_t)words; } inline void ParallelCompactData::RegionData::decrement_destination_count() { assert(_dc_and_los < dc_claimed, "already claimed"); assert(_dc_and_los >= dc_one, "count would go negative"); Atomic::add(dc_mask, &_dc_and_los); } inline HeapWord* ParallelCompactData::RegionData::data_location() const { DEBUG_ONLY(return _data_location;) NOT_DEBUG(return NULL;) } inline HeapWord* ParallelCompactData::RegionData::highest_ref() const { DEBUG_ONLY(return _highest_ref;) NOT_DEBUG(return NULL;) } inline void ParallelCompactData::RegionData::set_data_location(HeapWord* addr) { DEBUG_ONLY(_data_location = addr;) } inline void ParallelCompactData::RegionData::set_completed() { assert(claimed(), "must be claimed first"); _dc_and_los = dc_completed | (region_sz_t) live_obj_size(); } // MT-unsafe claiming of a region. Should only be used during single threaded // execution. inline bool ParallelCompactData::RegionData::claim_unsafe() { if (available()) { _dc_and_los |= dc_claimed; return true; } return false; } inline void ParallelCompactData::RegionData::add_live_obj(size_t words) { assert(words <= (size_t)los_mask - live_obj_size(), "overflow"); Atomic::add(static_cast(words), &_dc_and_los); } inline void ParallelCompactData::RegionData::set_highest_ref(HeapWord* addr) { #ifdef ASSERT HeapWord* tmp = _highest_ref; while (addr > tmp) { tmp = Atomic::cmpxchg(addr, &_highest_ref, tmp); } #endif // #ifdef ASSERT } inline bool ParallelCompactData::RegionData::claim() { const region_sz_t los = static_cast(live_obj_size()); const region_sz_t old = Atomic::cmpxchg(dc_claimed | los, &_dc_and_los, los); return old == los; } inline ParallelCompactData::RegionData* ParallelCompactData::region(size_t region_idx) const { assert(region_idx <= region_count(), "bad arg"); return _region_data + region_idx; } inline size_t ParallelCompactData::region(const RegionData* const region_ptr) const { assert(region_ptr >= _region_data, "bad arg"); assert(region_ptr <= _region_data + region_count(), "bad arg"); return pointer_delta(region_ptr, _region_data, sizeof(RegionData)); } inline ParallelCompactData::BlockData* ParallelCompactData::block(size_t n) const { assert(n < block_count(), "bad arg"); return _block_data + n; } inline size_t ParallelCompactData::region_offset(const HeapWord* addr) const { assert(addr >= _region_start, "bad addr"); assert(addr <= _region_end, "bad addr"); return (size_t(addr) & RegionAddrOffsetMask) >> LogHeapWordSize; } inline size_t ParallelCompactData::addr_to_region_idx(const HeapWord* addr) const { assert(addr >= _region_start, "bad addr " PTR_FORMAT " _region_start " PTR_FORMAT, p2i(addr), p2i(_region_start)); assert(addr <= _region_end, "bad addr " PTR_FORMAT " _region_end " PTR_FORMAT, p2i(addr), p2i(_region_end)); return pointer_delta(addr, _region_start) >> Log2RegionSize; } inline ParallelCompactData::RegionData* ParallelCompactData::addr_to_region_ptr(const HeapWord* addr) const { return region(addr_to_region_idx(addr)); } inline HeapWord* ParallelCompactData::region_to_addr(size_t region) const { assert(region <= _region_count, "region out of range"); return _region_start + (region << Log2RegionSize); } inline HeapWord* ParallelCompactData::region_to_addr(const RegionData* region) const { return region_to_addr(pointer_delta(region, _region_data, sizeof(RegionData))); } inline HeapWord* ParallelCompactData::region_to_addr(size_t region, size_t offset) const { assert(region <= _region_count, "region out of range"); assert(offset < RegionSize, "offset too big"); // This may be too strict. return region_to_addr(region) + offset; } inline HeapWord* ParallelCompactData::region_align_down(HeapWord* addr) const { assert(addr >= _region_start, "bad addr"); assert(addr < _region_end + RegionSize, "bad addr"); return (HeapWord*)(size_t(addr) & RegionAddrMask); } inline HeapWord* ParallelCompactData::region_align_up(HeapWord* addr) const { assert(addr >= _region_start, "bad addr"); assert(addr <= _region_end, "bad addr"); return region_align_down(addr + RegionSizeOffsetMask); } inline bool ParallelCompactData::is_region_aligned(HeapWord* addr) const { return region_offset(addr) == 0; } inline size_t ParallelCompactData::block_offset(const HeapWord* addr) const { assert(addr >= _region_start, "bad addr"); assert(addr <= _region_end, "bad addr"); return (size_t(addr) & BlockAddrOffsetMask) >> LogHeapWordSize; } inline size_t ParallelCompactData::addr_to_block_idx(const HeapWord* addr) const { assert(addr >= _region_start, "bad addr"); assert(addr <= _region_end, "bad addr"); return pointer_delta(addr, _region_start) >> Log2BlockSize; } inline ParallelCompactData::BlockData* ParallelCompactData::addr_to_block_ptr(const HeapWord* addr) const { return block(addr_to_block_idx(addr)); } inline HeapWord* ParallelCompactData::block_to_addr(size_t block) const { assert(block < _block_count, "block out of range"); return _region_start + (block << Log2BlockSize); } inline size_t ParallelCompactData::region_to_block_idx(size_t region) const { return region << Log2BlocksPerRegion; } inline HeapWord* ParallelCompactData::block_align_down(HeapWord* addr) const { assert(addr >= _region_start, "bad addr"); assert(addr < _region_end + RegionSize, "bad addr"); return (HeapWord*)(size_t(addr) & BlockAddrMask); } inline HeapWord* ParallelCompactData::block_align_up(HeapWord* addr) const { assert(addr >= _region_start, "bad addr"); assert(addr <= _region_end, "bad addr"); return block_align_down(addr + BlockSizeOffsetMask); } inline bool ParallelCompactData::is_block_aligned(HeapWord* addr) const { return block_offset(addr) == 0; } // Abstract closure for use with ParMarkBitMap::iterate(), which will invoke the // do_addr() method. // // The closure is initialized with the number of heap words to process // (words_remaining()), and becomes 'full' when it reaches 0. The do_addr() // methods in subclasses should update the total as words are processed. Since // only one subclass actually uses this mechanism to terminate iteration, the // default initial value is > 0. The implementation is here and not in the // single subclass that uses it to avoid making is_full() virtual, and thus // adding a virtual call per live object. class ParMarkBitMapClosure: public StackObj { public: typedef ParMarkBitMap::idx_t idx_t; typedef ParMarkBitMap::IterationStatus IterationStatus; public: inline ParMarkBitMapClosure(ParMarkBitMap* mbm, ParCompactionManager* cm, size_t words = max_uintx); inline ParCompactionManager* compaction_manager() const; inline ParMarkBitMap* bitmap() const; inline size_t words_remaining() const; inline bool is_full() const; inline HeapWord* source() const; inline void set_source(HeapWord* addr); virtual IterationStatus do_addr(HeapWord* addr, size_t words) = 0; protected: inline void decrement_words_remaining(size_t words); private: ParMarkBitMap* const _bitmap; ParCompactionManager* const _compaction_manager; DEBUG_ONLY(const size_t _initial_words_remaining;) // Useful in debugger. size_t _words_remaining; // Words left to copy. protected: HeapWord* _source; // Next addr that would be read. }; inline ParMarkBitMapClosure::ParMarkBitMapClosure(ParMarkBitMap* bitmap, ParCompactionManager* cm, size_t words): _bitmap(bitmap), _compaction_manager(cm) #ifdef ASSERT , _initial_words_remaining(words) #endif { _words_remaining = words; _source = NULL; } inline ParCompactionManager* ParMarkBitMapClosure::compaction_manager() const { return _compaction_manager; } inline ParMarkBitMap* ParMarkBitMapClosure::bitmap() const { return _bitmap; } inline size_t ParMarkBitMapClosure::words_remaining() const { return _words_remaining; } inline bool ParMarkBitMapClosure::is_full() const { return words_remaining() == 0; } inline HeapWord* ParMarkBitMapClosure::source() const { return _source; } inline void ParMarkBitMapClosure::set_source(HeapWord* addr) { _source = addr; } inline void ParMarkBitMapClosure::decrement_words_remaining(size_t words) { assert(_words_remaining >= words, "processed too many words"); _words_remaining -= words; } // The UseParallelOldGC collector is a stop-the-world garbage collector that // does parts of the collection using parallel threads. The collection includes // the tenured generation and the young generation. The permanent generation is // collected at the same time as the other two generations but the permanent // generation is collect by a single GC thread. The permanent generation is // collected serially because of the requirement that during the processing of a // klass AAA, any objects reference by AAA must already have been processed. // This requirement is enforced by a left (lower address) to right (higher // address) sliding compaction. // // There are four phases of the collection. // // - marking phase // - summary phase // - compacting phase // - clean up phase // // Roughly speaking these phases correspond, respectively, to // - mark all the live objects // - calculate the destination of each object at the end of the collection // - move the objects to their destination // - update some references and reinitialize some variables // // These three phases are invoked in PSParallelCompact::invoke_no_policy(). The // marking phase is implemented in PSParallelCompact::marking_phase() and does a // complete marking of the heap. The summary phase is implemented in // PSParallelCompact::summary_phase(). The move and update phase is implemented // in PSParallelCompact::compact(). // // A space that is being collected is divided into regions and with each region // is associated an object of type ParallelCompactData. Each region is of a // fixed size and typically will contain more than 1 object and may have parts // of objects at the front and back of the region. // // region -----+---------------------+---------- // objects covered [ AAA )[ BBB )[ CCC )[ DDD ) // // The marking phase does a complete marking of all live objects in the heap. // The marking also compiles the size of the data for all live objects covered // by the region. This size includes the part of any live object spanning onto // the region (part of AAA if it is live) from the front, all live objects // contained in the region (BBB and/or CCC if they are live), and the part of // any live objects covered by the region that extends off the region (part of // DDD if it is live). The marking phase uses multiple GC threads and marking // is done in a bit array of type ParMarkBitMap. The marking of the bit map is // done atomically as is the accumulation of the size of the live objects // covered by a region. // // The summary phase calculates the total live data to the left of each region // XXX. Based on that total and the bottom of the space, it can calculate the // starting location of the live data in XXX. The summary phase calculates for // each region XXX quantities such as // // - the amount of live data at the beginning of a region from an object // entering the region. // - the location of the first live data on the region // - a count of the number of regions receiving live data from XXX. // // See ParallelCompactData for precise details. The summary phase also // calculates the dense prefix for the compaction. The dense prefix is a // portion at the beginning of the space that is not moved. The objects in the // dense prefix do need to have their object references updated. See method // summarize_dense_prefix(). // // The summary phase is done using 1 GC thread. // // The compaction phase moves objects to their new location and updates all // references in the object. // // A current exception is that objects that cross a region boundary are moved // but do not have their references updated. References are not updated because // it cannot easily be determined if the klass pointer KKK for the object AAA // has been updated. KKK likely resides in a region to the left of the region // containing AAA. These AAA's have there references updated at the end in a // clean up phase. See the method PSParallelCompact::update_deferred_objects(). // An alternate strategy is being investigated for this deferral of updating. // // Compaction is done on a region basis. A region that is ready to be filled is // put on a ready list and GC threads take region off the list and fill them. A // region is ready to be filled if it empty of live objects. Such a region may // have been initially empty (only contained dead objects) or may have had all // its live objects copied out already. A region that compacts into itself is // also ready for filling. The ready list is initially filled with empty // regions and regions compacting into themselves. There is always at least 1 // region that can be put on the ready list. The regions are atomically added // and removed from the ready list. class PSParallelCompact : AllStatic { public: // Convenient access to type names. typedef ParMarkBitMap::idx_t idx_t; typedef ParallelCompactData::RegionData RegionData; typedef ParallelCompactData::BlockData BlockData; typedef enum { old_space_id, eden_space_id, from_space_id, to_space_id, last_space_id } SpaceId; public: // Inline closure decls // class IsAliveClosure: public BoolObjectClosure { public: virtual bool do_object_b(oop p); }; friend class RefProcTaskProxy; friend class PSParallelCompactTest; private: static STWGCTimer _gc_timer; static ParallelOldTracer _gc_tracer; static elapsedTimer _accumulated_time; static unsigned int _total_invocations; static unsigned int _maximum_compaction_gc_num; static jlong _time_of_last_gc; // ms static CollectorCounters* _counters; static ParMarkBitMap _mark_bitmap; static ParallelCompactData _summary_data; static IsAliveClosure _is_alive_closure; static SpaceInfo _space_info[last_space_id]; // Reference processing (used in ...follow_contents) static SpanSubjectToDiscoveryClosure _span_based_discoverer; static ReferenceProcessor* _ref_processor; // Values computed at initialization and used by dead_wood_limiter(). static double _dwl_mean; static double _dwl_std_dev; static double _dwl_first_term; static double _dwl_adjustment; #ifdef ASSERT static bool _dwl_initialized; #endif // #ifdef ASSERT public: static ParallelOldTracer* gc_tracer() { return &_gc_tracer; } private: static void initialize_space_info(); // Clear the marking bitmap and summary data that cover the specified space. static void clear_data_covering_space(SpaceId id); static void pre_compact(); static void post_compact(); // Mark live objects static void marking_phase(ParCompactionManager* cm, bool maximum_heap_compaction, ParallelOldTracer *gc_tracer); // Compute the dense prefix for the designated space. This is an experimental // implementation currently not used in production. static HeapWord* compute_dense_prefix_via_density(const SpaceId id, bool maximum_compaction); // Methods used to compute the dense prefix. // Compute the value of the normal distribution at x = density. The mean and // standard deviation are values saved by initialize_dead_wood_limiter(). static inline double normal_distribution(double density); // Initialize the static vars used by dead_wood_limiter(). static void initialize_dead_wood_limiter(); // Return the percentage of space that can be treated as "dead wood" (i.e., // not reclaimed). static double dead_wood_limiter(double density, size_t min_percent); // Find the first (left-most) region in the range [beg, end) that has at least // dead_words of dead space to the left. The argument beg must be the first // region in the space that is not completely live. static RegionData* dead_wood_limit_region(const RegionData* beg, const RegionData* end, size_t dead_words); // Return a pointer to the first region in the range [beg, end) that is not // completely full. static RegionData* first_dead_space_region(const RegionData* beg, const RegionData* end); // Return a value indicating the benefit or 'yield' if the compacted region // were to start (or equivalently if the dense prefix were to end) at the // candidate region. Higher values are better. // // The value is based on the amount of space reclaimed vs. the costs of (a) // updating references in the dense prefix plus (b) copying objects and // updating references in the compacted region. static inline double reclaimed_ratio(const RegionData* const candidate, HeapWord* const bottom, HeapWord* const top, HeapWord* const new_top); // Compute the dense prefix for the designated space. static HeapWord* compute_dense_prefix(const SpaceId id, bool maximum_compaction); // Return true if dead space crosses onto the specified Region; bit must be // the bit index corresponding to the first word of the Region. static inline bool dead_space_crosses_boundary(const RegionData* region, idx_t bit); // Summary phase utility routine to fill dead space (if any) at the dense // prefix boundary. Should only be called if the the dense prefix is // non-empty. static void fill_dense_prefix_end(SpaceId id); static void summarize_spaces_quick(); static void summarize_space(SpaceId id, bool maximum_compaction); static void summary_phase(ParCompactionManager* cm, bool maximum_compaction); // Adjust addresses in roots. Does not adjust addresses in heap. static void adjust_roots(ParCompactionManager* cm); DEBUG_ONLY(static void write_block_fill_histogram();) // Move objects to new locations. static void compact_perm(ParCompactionManager* cm); static void compact(); // Add available regions to the stack and draining tasks to the task queue. static void prepare_region_draining_tasks(GCTaskQueue* q, uint parallel_gc_threads); // Add dense prefix update tasks to the task queue. static void enqueue_dense_prefix_tasks(GCTaskQueue* q, uint parallel_gc_threads); // Add region stealing tasks to the task queue. static void enqueue_region_stealing_tasks( GCTaskQueue* q, ParallelTaskTerminator* terminator_ptr, uint parallel_gc_threads); // If objects are left in eden after a collection, try to move the boundary // and absorb them into the old gen. Returns true if eden was emptied. static bool absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy, PSYoungGen* young_gen, PSOldGen* old_gen); // Reset time since last full gc static void reset_millis_since_last_gc(); #ifndef PRODUCT // Print generic summary data static void print_generic_summary_data(ParallelCompactData& summary_data, HeapWord* const beg_addr, HeapWord* const end_addr); #endif // #ifndef PRODUCT public: PSParallelCompact(); static void invoke(bool maximum_heap_compaction); static bool invoke_no_policy(bool maximum_heap_compaction); static void post_initialize(); // Perform initialization for PSParallelCompact that requires // allocations. This should be called during the VM initialization // at a pointer where it would be appropriate to return a JNI_ENOMEM // in the event of a failure. static bool initialize(); // Closure accessors static BoolObjectClosure* is_alive_closure() { return (BoolObjectClosure*)&_is_alive_closure; } // Public accessors static elapsedTimer* accumulated_time() { return &_accumulated_time; } static unsigned int total_invocations() { return _total_invocations; } static CollectorCounters* counters() { return _counters; } // Used to add tasks static GCTaskManager* const gc_task_manager(); // Marking support static inline bool mark_obj(oop obj); static inline bool is_marked(oop obj); template static inline void adjust_pointer(T* p, ParCompactionManager* cm); // Compaction support. // Return true if p is in the range [beg_addr, end_addr). static inline bool is_in(HeapWord* p, HeapWord* beg_addr, HeapWord* end_addr); static inline bool is_in(oop* p, HeapWord* beg_addr, HeapWord* end_addr); // Convenience wrappers for per-space data kept in _space_info. static inline MutableSpace* space(SpaceId space_id); static inline HeapWord* new_top(SpaceId space_id); static inline HeapWord* dense_prefix(SpaceId space_id); static inline ObjectStartArray* start_array(SpaceId space_id); // Move and update the live objects in the specified space. static void move_and_update(ParCompactionManager* cm, SpaceId space_id); // Process the end of the given region range in the dense prefix. // This includes saving any object not updated. static void dense_prefix_regions_epilogue(ParCompactionManager* cm, size_t region_start_index, size_t region_end_index, idx_t exiting_object_offset, idx_t region_offset_start, idx_t region_offset_end); // Update a region in the dense prefix. For each live object // in the region, update it's interior references. For each // dead object, fill it with deadwood. Dead space at the end // of a region range will be filled to the start of the next // live object regardless of the region_index_end. None of the // objects in the dense prefix move and dead space is dead // (holds only dead objects that don't need any processing), so // dead space can be filled in any order. static void update_and_deadwood_in_dense_prefix(ParCompactionManager* cm, SpaceId space_id, size_t region_index_start, size_t region_index_end); // Return the address of the count + 1st live word in the range [beg, end). static HeapWord* skip_live_words(HeapWord* beg, HeapWord* end, size_t count); // Return the address of the word to be copied to dest_addr, which must be // aligned to a region boundary. static HeapWord* first_src_addr(HeapWord* const dest_addr, SpaceId src_space_id, size_t src_region_idx); // Determine the next source region, set closure.source() to the start of the // new region return the region index. Parameter end_addr is the address one // beyond the end of source range just processed. If necessary, switch to a // new source space and set src_space_id (in-out parameter) and src_space_top // (out parameter) accordingly. static size_t next_src_region(MoveAndUpdateClosure& closure, SpaceId& src_space_id, HeapWord*& src_space_top, HeapWord* end_addr); // Decrement the destination count for each non-empty source region in the // range [beg_region, region(region_align_up(end_addr))). If the destination // count for a region goes to 0 and it needs to be filled, enqueue it. static void decrement_destination_counts(ParCompactionManager* cm, SpaceId src_space_id, size_t beg_region, HeapWord* end_addr); // Fill a region, copying objects from one or more source regions. static void fill_region(ParCompactionManager* cm, size_t region_idx); static void fill_and_update_region(ParCompactionManager* cm, size_t region) { fill_region(cm, region); } // Fill in the block table for the specified region. static void fill_blocks(size_t region_idx); // Update the deferred objects in the space. static void update_deferred_objects(ParCompactionManager* cm, SpaceId id); static ParMarkBitMap* mark_bitmap() { return &_mark_bitmap; } static ParallelCompactData& summary_data() { return _summary_data; } // Reference Processing static ReferenceProcessor* const ref_processor() { return _ref_processor; } static STWGCTimer* gc_timer() { return &_gc_timer; } // Return the SpaceId for the given address. static SpaceId space_id(HeapWord* addr); // Time since last full gc (in milliseconds). static jlong millis_since_last_gc(); static void print_on_error(outputStream* st); #ifndef PRODUCT // Debugging support. static const char* space_names[last_space_id]; static void print_region_ranges(); static void print_dense_prefix_stats(const char* const algorithm, const SpaceId id, const bool maximum_compaction, HeapWord* const addr); static void summary_phase_msg(SpaceId dst_space_id, HeapWord* dst_beg, HeapWord* dst_end, SpaceId src_space_id, HeapWord* src_beg, HeapWord* src_end); #endif // #ifndef PRODUCT #ifdef ASSERT // Sanity check the new location of a word in the heap. static inline void check_new_location(HeapWord* old_addr, HeapWord* new_addr); // Verify that all the regions have been emptied. static void verify_complete(SpaceId space_id); #endif // #ifdef ASSERT }; class MoveAndUpdateClosure: public ParMarkBitMapClosure { public: inline MoveAndUpdateClosure(ParMarkBitMap* bitmap, ParCompactionManager* cm, ObjectStartArray* start_array, HeapWord* destination, size_t words); // Accessors. HeapWord* destination() const { return _destination; } // If the object will fit (size <= words_remaining()), copy it to the current // destination, update the interior oops and the start array and return either // full (if the closure is full) or incomplete. If the object will not fit, // return would_overflow. virtual IterationStatus do_addr(HeapWord* addr, size_t size); // Copy enough words to fill this closure, starting at source(). Interior // oops and the start array are not updated. Return full. IterationStatus copy_until_full(); // Copy enough words to fill this closure or to the end of an object, // whichever is smaller, starting at source(). Interior oops and the start // array are not updated. void copy_partial_obj(); protected: // Update variables to indicate that word_count words were processed. inline void update_state(size_t word_count); protected: ObjectStartArray* const _start_array; HeapWord* _destination; // Next addr to be written. }; inline MoveAndUpdateClosure::MoveAndUpdateClosure(ParMarkBitMap* bitmap, ParCompactionManager* cm, ObjectStartArray* start_array, HeapWord* destination, size_t words) : ParMarkBitMapClosure(bitmap, cm, words), _start_array(start_array) { _destination = destination; } inline void MoveAndUpdateClosure::update_state(size_t words) { decrement_words_remaining(words); _source += words; _destination += words; } class UpdateOnlyClosure: public ParMarkBitMapClosure { private: const PSParallelCompact::SpaceId _space_id; ObjectStartArray* const _start_array; public: UpdateOnlyClosure(ParMarkBitMap* mbm, ParCompactionManager* cm, PSParallelCompact::SpaceId space_id); // Update the object. virtual IterationStatus do_addr(HeapWord* addr, size_t words); inline void do_addr(HeapWord* addr); }; class FillClosure: public ParMarkBitMapClosure { public: FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id); virtual IterationStatus do_addr(HeapWord* addr, size_t size); private: ObjectStartArray* const _start_array; }; #endif // SHARE_VM_GC_PARALLEL_PSPARALLELCOMPACT_HPP