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*/
- #ifndef GC_SHARED_FULLGCFORWARDING_INLINE_HPP
- #define GC_SHARED_FULLGCFORWARDING_INLINE_HPP
+ #ifndef SHARE_GC_SHARED_FULLGCFORWARDING_INLINE_HPP
+ #define SHARE_GC_SHARED_FULLGCFORWARDING_INLINE_HPP
#include "gc/shared/fullGCForwarding.hpp"
-
+ #include "logging/log.hpp"
+ #include "nmt/memTag.hpp"
+ #include "oops/markWord.hpp"
#include "oops/oop.inline.hpp"
- #include "utilities/globalDefinitions.hpp"
+ #include "utilities/concurrentHashTable.inline.hpp"
+ #include "utilities/fastHash.hpp"
+ #include "utilities/macros.hpp"
+ #include "utilities/powerOfTwo.hpp"
+
+ // We cannot use 0, because that may already be a valid base address in zero-based heaps.
+ // 0x1 is safe because heap base addresses must be aligned by much larger alignment
+ template <int BITS>
+ HeapWord* const FullGCForwardingImpl<BITS>::UNUSED_BASE = reinterpret_cast<HeapWord*>(0x1);
+
+ template <int BITS>
+ HeapWord* FullGCForwardingImpl<BITS>::_heap_start = nullptr;
+ template <int BITS>
+ size_t FullGCForwardingImpl<BITS>::_heap_start_region_bias = 0;
+ template <int BITS>
+ size_t FullGCForwardingImpl<BITS>::_num_regions = 0;
+ template <int BITS>
+ uintptr_t FullGCForwardingImpl<BITS>::_region_mask = 0;
+ template <int BITS>
+ HeapWord** FullGCForwardingImpl<BITS>::_biased_bases = nullptr;
+ template <int BITS>
+ HeapWord** FullGCForwardingImpl<BITS>::_bases_table = nullptr;
+ template <int BITS>
+ size_t FullGCForwardingImpl<BITS>::_fallback_table_log2_start_size = 9; // 512 entries.
+ template <int BITS>
+ FallbackTable* FullGCForwardingImpl<BITS>::_fallback_table = nullptr;
+ #ifndef PRODUCT
+ template <int BITS>
+ volatile uint64_t FullGCForwardingImpl<BITS>::_num_forwardings = 0;
+ template <int BITS>
+ volatile uint64_t FullGCForwardingImpl<BITS>::_num_fallback_forwardings = 0;
+ #endif
+
+ template <int BITS>
+ bool FullGCForwardingImpl<BITS>::is_forwarded(oop obj) {
+ return obj->is_forwarded();
+ }
+
+ template <int BITS>
+ size_t FullGCForwardingImpl<BITS>::biased_region_index_containing(HeapWord* addr) {
+ return reinterpret_cast<uintptr_t>(addr) >> BLOCK_SIZE_BYTES_SHIFT;
+ }
+
+ template <int BITS>
+ bool FullGCForwardingImpl<BITS>::is_fallback(uintptr_t encoded) {
+ return (encoded & OFFSET_MASK) == FALLBACK_PATTERN_IN_PLACE;
+ }
+
+ template <int BITS>
+ uintptr_t FullGCForwardingImpl<BITS>::encode_forwarding(HeapWord* from, HeapWord* to) {
+ size_t from_block_idx = biased_region_index_containing(from);
+
+ HeapWord* to_region_base = _biased_bases[from_block_idx];
+ if (to_region_base == UNUSED_BASE) {
+ HeapWord* prev = Atomic::cmpxchg(&_biased_bases[from_block_idx], UNUSED_BASE, to);
+ if (prev == UNUSED_BASE) {
+ to_region_base = to;
+ } else {
+ to_region_base = prev;
+ }
+ // _biased_bases[from_block_idx] = to_region_base = to;
+ }
+ // Avoid pointer_delta() on purpose: using an unsigned subtraction,
+ // we get an underflow when to < to_region_base, which means
+ // we can use a single comparison instead of:
+ // if (to_region_base > to || (to - to_region_base) > MAX_OFFSET) { .. }
+ size_t offset = static_cast<size_t>(to - to_region_base);
+ if (offset > MAX_OFFSET) {
+ offset = FALLBACK_PATTERN;
+ }
+ uintptr_t encoded = (offset << OFFSET_BITS_SHIFT) | markWord::marked_value;
+
+ assert(is_fallback(encoded) || to == decode_forwarding(from, encoded), "must be reversible: " PTR_FORMAT " -> " PTR_FORMAT ", reversed: " PTR_FORMAT ", encoded: " INTPTR_FORMAT ", to_region_base: " PTR_FORMAT ", from_block_idx: %lu", p2i(from), p2i(to), p2i(decode_forwarding(from, encoded)), encoded, p2i(to_region_base), from_block_idx);
+ assert((encoded & ~AVAILABLE_BITS_MASK) == 0, "must encode to available bits");
+ return encoded;
+ }
- void FullGCForwarding::forward_to(oop from, oop to) {
+ template <int BITS>
+ HeapWord* FullGCForwardingImpl<BITS>::decode_forwarding(HeapWord* from, uintptr_t encoded) {
+ assert(!is_fallback(encoded), "must not be fallback-forwarded, encoded: " INTPTR_FORMAT ", OFFSET_MASK: " INTPTR_FORMAT ", FALLBACK_PATTERN_IN_PLACE: " INTPTR_FORMAT, encoded, OFFSET_MASK, FALLBACK_PATTERN_IN_PLACE);
+ assert((encoded & ~AVAILABLE_BITS_MASK) == 0, "must decode from available bits, encoded: " INTPTR_FORMAT, encoded);
+ uintptr_t offset = (encoded >> OFFSET_BITS_SHIFT);
+
+ size_t from_idx = biased_region_index_containing(from);
+ HeapWord* base = _biased_bases[from_idx];
+ assert(base != UNUSED_BASE, "must not be unused base: encoded: " INTPTR_FORMAT, encoded);
+ HeapWord* decoded = base + offset;
+ assert(decoded >= _heap_start,
+ "Address must be above heap start. encoded: " INTPTR_FORMAT ", base: " PTR_FORMAT,
+ encoded, p2i(base));
+
+ return decoded;
+ }
+
+ template <int BITS>
+ void FullGCForwardingImpl<BITS>::forward_to_impl(oop from, oop to) {
+ assert(_bases_table != nullptr, "call begin() before forwarding");
+
+ markWord from_header = from->mark();
+ HeapWord* from_hw = cast_from_oop<HeapWord*>(from);
+ HeapWord* to_hw = cast_from_oop<HeapWord*>(to);
+ uintptr_t encoded = encode_forwarding(from_hw, to_hw);
+ markWord new_header = markWord((from_header.value() & ~OFFSET_MASK) | encoded);
+ from->set_mark(new_header);
+
+ if (is_fallback(encoded)) {
+ fallback_forward_to(from_hw, to_hw);
+ }
+ NOT_PRODUCT(Atomic::inc(&_num_forwardings);)
+ }
+
+ template <int BITS>
+ void FullGCForwardingImpl<BITS>::forward_to(oop obj, oop fwd) {
+ assert(fwd != nullptr, "no null forwarding");
#ifdef _LP64
- uintptr_t encoded = pointer_delta(cast_from_oop<HeapWord*>(to), _heap_base) << Shift;
- assert(encoded <= static_cast<uintptr_t>(right_n_bits(_num_low_bits)), "encoded forwardee must fit");
- uintptr_t mark = from->mark().value();
- mark &= ~right_n_bits(_num_low_bits);
- mark |= (encoded | markWord::marked_value);
- from->set_mark(markWord(mark));
+ assert(_bases_table != nullptr, "expect sliding forwarding initialized");
+ forward_to_impl(obj, fwd);
+ // assert(forwardee(obj) == fwd, "must be forwarded to correct forwardee, obj: " PTR_FORMAT ", forwardee(obj): " PTR_FORMAT ", fwd: " PTR_FORMAT ", mark: " INTPTR_FORMAT ", num-regions: %lu, base: " PTR_FORMAT ", OFFSET_MASK: " INTPTR_FORMAT ", encoded: " PTR_FORMAT ", biased-base: " PTR_FORMAT ", heap-start: " PTR_FORMAT, p2i(obj), p2i(forwardee(obj)), p2i(fwd), obj->mark().value(), _num_regions, p2i(_bases_table[0]), OFFSET_MASK, encode_forwarding(cast_from_oop<HeapWord*>(obj), cast_from_oop<HeapWord*>(fwd)), p2i(_biased_bases[biased_region_index_containing(cast_from_oop<HeapWord*>(obj))]), p2i(_heap_start));
#else
- from->forward_to(to);
+ obj->forward_to(fwd);
#endif
}
- oop FullGCForwarding::forwardee(oop from) {
+ template <int BITS>
+ oop FullGCForwardingImpl<BITS>::forwardee_impl(oop from) {
+ assert(_bases_table != nullptr, "call begin() before asking for forwarding");
+
+ markWord header = from->mark();
+ HeapWord* from_hw = cast_from_oop<HeapWord*>(from);
+ if (is_fallback(header.value())) {
+ HeapWord* to = fallback_forwardee(from_hw);
+ return cast_to_oop(to);
+ }
+ uintptr_t encoded = header.value() & OFFSET_MASK;
+ HeapWord* to = decode_forwarding(from_hw, encoded);
+ return cast_to_oop(to);
+ }
+
+ template <int BITS>
+ oop FullGCForwardingImpl<BITS>::forwardee(oop obj) {
#ifdef _LP64
- uintptr_t mark = from->mark().value();
- HeapWord* decoded = _heap_base + ((mark & right_n_bits(_num_low_bits)) >> Shift);
- return cast_to_oop(decoded);
+ assert(_bases_table != nullptr, "expect sliding forwarding initialized");
+ return forwardee_impl(obj);
#else
- return from->forwardee();
+ return obj->forwardee();
+ #endif
+ }
+
+ static uintx hash(HeapWord* const& addr) {
+ uint64_t val = reinterpret_cast<uint64_t>(addr);
+ uint32_t hash = FastHash::get_hash32(static_cast<uint32_t>(val), static_cast<uint32_t>(val >> 32));
+ return hash;
+ }
+
+ struct ForwardingEntry {
+ HeapWord* _from;
+ HeapWord* _to;
+ ForwardingEntry(HeapWord* from, HeapWord* to) : _from(from), _to(to) {}
+ };
+
+ struct FallbackTableConfig {
+ using Value = ForwardingEntry;
+ static uintx get_hash(Value const& entry, bool* is_dead) {
+ return hash(entry._from);
+ }
+ static void* allocate_node(void* context, size_t size, Value const& value) {
+ return AllocateHeap(size, mtGC);
+ }
+ static void free_node(void* context, void* memory, Value const& value) {
+ FreeHeap(memory);
+ }
+ };
+
+ class FallbackTable : public ConcurrentHashTable<FallbackTableConfig, mtGC> {
+ public:
+ explicit FallbackTable(size_t log2size) : ConcurrentHashTable(log2size) {}
+ };
+
+ class FallbackTableLookup : public StackObj {
+ ForwardingEntry const _entry;
+ public:
+ explicit FallbackTableLookup(HeapWord* from) : _entry(from, nullptr) {}
+ uintx get_hash() const {
+ return hash(_entry._from);
+ }
+ bool equals(const ForwardingEntry* value) const {
+ return _entry._from == value->_from;
+ }
+ static bool is_dead(ForwardingEntry* value) { return false; }
+ };
+
+ template <int BITS>
+ void FullGCForwardingImpl<BITS>::initialize(MemRegion heap) {
+ #ifdef _LP64
+ _heap_start = heap.start();
+
+ size_t rounded_heap_size = MAX2(round_up_power_of_2(heap.byte_size()) / BytesPerWord, BLOCK_SIZE_WORDS);
+
+ _num_regions = rounded_heap_size / BLOCK_SIZE_WORDS;
+
+ _heap_start_region_bias = reinterpret_cast<uintptr_t>(_heap_start) >> BLOCK_SIZE_BYTES_SHIFT;
+ _region_mask = ~((static_cast<uintptr_t>(1) << BLOCK_SIZE_BYTES_SHIFT) - 1);
+
+ assert(_bases_table == nullptr, "should not be initialized yet");
+ assert(_fallback_table == nullptr, "should not be initialized yet");
+ #endif
+ }
+
+ template <int BITS>
+ void FullGCForwardingImpl<BITS>::begin() {
+ #ifdef _LP64
+ assert(_bases_table == nullptr, "should not be initialized yet");
+ assert(_fallback_table == nullptr, "should not be initialized yet");
+
+ _fallback_table = nullptr;
+
+ #ifndef PRODUCT
+ _num_forwardings = 0;
+ _num_fallback_forwardings = 0;
+ #endif
+
+ size_t max = _num_regions;
+ _bases_table = NEW_C_HEAP_ARRAY(HeapWord*, max, mtGC);
+ HeapWord** biased_start = _bases_table - _heap_start_region_bias;
+ _biased_bases = biased_start;
+ if (max == 1) {
+ // Optimize the case when the block-size >= heap-size.
+ // In this case we can use the heap-start as block-start,
+ // and don't risk that competing GC threads set a higher
+ // address as block-start, which would lead to unnecessary
+ // fallback-usage.
+ _bases_table[0] = _heap_start;
+ } else {
+ for (size_t i = 0; i < max; i++) {
+ _bases_table[i] = UNUSED_BASE;
+ }
+ }
+ #endif
+ }
+
+ template <int BITS>
+ void FullGCForwardingImpl<BITS>::end() {
+ #ifndef PRODUCT
+ size_t fallback_table_size = _fallback_table != nullptr ? _fallback_table->get_mem_size(Thread::current()) : 0;
+ log_info(gc)("Total forwardings: " UINT64_FORMAT ", fallback forwardings: " UINT64_FORMAT
+ ", ratio: %f, memory used by fallback table: %zu%s, memory used by bases table: %zu%s",
+ _num_forwardings, _num_fallback_forwardings, static_cast<float>(_num_forwardings) / static_cast<float>(_num_fallback_forwardings),
+ byte_size_in_proper_unit(fallback_table_size),
+ proper_unit_for_byte_size(fallback_table_size),
+ byte_size_in_proper_unit(sizeof(HeapWord*) * _num_regions),
+ proper_unit_for_byte_size(sizeof(HeapWord*) * _num_regions));
+ #endif
+ #ifdef _LP64
+ assert(_bases_table != nullptr, "should be initialized");
+ FREE_C_HEAP_ARRAY(HeapWord*, _bases_table);
+ _bases_table = nullptr;
+ if (_fallback_table != nullptr) {
+ delete _fallback_table;
+ _fallback_table = nullptr;
+ }
+ #endif
+ }
+
+ template <int BITS>
+ void FullGCForwardingImpl<BITS>::maybe_init_fallback_table() {
+ if (_fallback_table == nullptr) {
+ FallbackTable* fallback_table = new FallbackTable(_fallback_table_log2_start_size);
+ FallbackTable* prev = Atomic::cmpxchg(&_fallback_table, static_cast<FallbackTable*>(nullptr), fallback_table);
+ if (prev != nullptr) {
+ // Another thread won, discard our table.
+ delete fallback_table;
+ }
+ }
+ }
+
+ template <int BITS>
+ void FullGCForwardingImpl<BITS>::fallback_forward_to(HeapWord* from, HeapWord* to) {
+ assert(to != nullptr, "no null forwarding");
+ maybe_init_fallback_table();
+ assert(_fallback_table != nullptr, "should be initialized");
+ FallbackTableLookup lookup_f(from);
+ ForwardingEntry entry(from, to);
+ auto found_f = [&](ForwardingEntry* found) {
+ // If dupe has been found, override it with new value.
+ // This is also called when new entry is succussfully inserted.
+ if (found->_to != to) {
+ found->_to = to;
+ }
+ };
+ Thread* current_thread = Thread::current();
+ bool grow;
+ bool added = _fallback_table->insert_get(current_thread, lookup_f, entry, found_f, &grow);
+ NOT_PRODUCT(Atomic::inc(&_num_fallback_forwardings);)
+ #ifdef ASSERT
+ assert(fallback_forwardee(from) != nullptr, "must have entered forwarding");
+ assert(fallback_forwardee(from) == to, "forwarding must be correct, added: %s, from: " PTR_FORMAT ", to: " PTR_FORMAT ", fwd: " PTR_FORMAT, BOOL_TO_STR(added), p2i(from), p2i(to), p2i(fallback_forwardee(from)));
#endif
+ if (grow) {
+ _fallback_table->grow(current_thread);
+ log_debug(gc)("grow fallback table to size: %zu bytes", _fallback_table->get_mem_size(current_thread));
+ }
}
- bool FullGCForwarding::is_forwarded(oop obj) {
- return obj->mark().is_forwarded();
+ template <int BITS>
+ HeapWord* FullGCForwardingImpl<BITS>::fallback_forwardee(HeapWord* from) {
+ assert(_fallback_table != nullptr, "fallback table must be present");
+ HeapWord* result;
+ FallbackTableLookup lookup_f(from);
+ auto found_f = [&](const ForwardingEntry* found) {
+ result = found->_to;
+ };
+ bool found = _fallback_table->get(Thread::current(), lookup_f, found_f);
+ assert(found, "something must have been found");
+ assert(result != nullptr, "must have found forwarding");
+ return result;
}
- #endif // GC_SHARED_FULLGCFORWARDING_INLINE_HPP
+ #endif // SHARE_GC_SHARED_FULLGCFORWARDING_INLINE_HPP
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