8234740: Harmonize parameter order in Atomic - cmpxchg
Reviewed-by: rehn, dholmes
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#ifndef SHARE_GC_PARALLEL_PSPARALLELCOMPACT_HPP
#define SHARE_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 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_and_los, dc_mask);
}
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(&_dc_and_los, static_cast<region_sz_t>(words));
}
inline void ParallelCompactData::RegionData::set_highest_ref(HeapWord* addr)
{
#ifdef ASSERT
HeapWord* tmp = _highest_ref;
while (addr > tmp) {
tmp = Atomic::cmpxchg(&_highest_ref, tmp, addr);
}
#endif // #ifdef ASSERT
}
inline bool ParallelCompactData::RegionData::claim()
{
const region_sz_t los = static_cast<region_sz_t>(live_obj_size());
const region_sz_t old = Atomic::cmpxchg(&_dc_and_los, los, dc_claimed | 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 TaskQueue;
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;
struct UpdateDensePrefixTask : public CHeapObj<mtGC> {
SpaceId _space_id;
size_t _region_index_start;
size_t _region_index_end;
UpdateDensePrefixTask() :
_space_id(SpaceId(0)),
_region_index_start(0),
_region_index_end(0) {}
UpdateDensePrefixTask(SpaceId space_id,
size_t region_index_start,
size_t region_index_end) :
_space_id(space_id),
_region_index_start(region_index_start),
_region_index_end(region_index_end) {}
};
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(uint parallel_gc_threads);
// Add dense prefix update tasks to the task queue.
static void enqueue_dense_prefix_tasks(TaskQueue& task_queue,
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; }
// Marking support
static inline bool mark_obj(oop obj);
static inline bool is_marked(oop obj);
template <class T> 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);
// 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_GC_PARALLEL_PSPARALLELCOMPACT_HPP