mirror of
https://github.com/RGBCube/serenity
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05c80cac20
Don't visit cells that are already marked. This prevents the marking phase from looping forever when two cells refer to each other. Also do the marking directly from the CellVisitor, removing another unnecessary phase of the collector. :^)
128 lines
3.4 KiB
C++
128 lines
3.4 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <AK/Badge.h>
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#include <AK/HashTable.h>
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#include <LibJS/Heap.h>
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#include <LibJS/HeapBlock.h>
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#include <LibJS/Interpreter.h>
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#include <LibJS/Object.h>
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#define HEAP_DEBUG
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namespace JS {
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Heap::Heap(Interpreter& interpreter)
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: m_interpreter(interpreter)
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{
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}
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Heap::~Heap()
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{
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}
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Cell* Heap::allocate_cell(size_t size)
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{
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for (auto& block : m_blocks) {
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if (size > block->cell_size())
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continue;
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if (auto* cell = block->allocate())
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return cell;
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}
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auto* block = (HeapBlock*)malloc(HeapBlock::block_size);
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new (block) HeapBlock(size);
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m_blocks.append(NonnullOwnPtr<HeapBlock>(NonnullOwnPtr<HeapBlock>::Adopt, *block));
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return block->allocate();
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}
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void Heap::collect_garbage()
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{
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HashTable<Cell*> roots;
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collect_roots(roots);
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mark_live_cells(roots);
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sweep_dead_cells();
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}
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void Heap::collect_roots(HashTable<Cell*>& roots)
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{
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m_interpreter.collect_roots({}, roots);
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#ifdef HEAP_DEBUG
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dbg() << "collect_roots:";
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for (auto* root : roots) {
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dbg() << " + " << root;
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}
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#endif
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}
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class MarkingVisitor final : public Cell::Visitor {
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public:
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MarkingVisitor() {}
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virtual void visit(Cell* cell)
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{
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if (cell->is_marked())
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return;
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#ifdef HEAP_DEBUG
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dbg() << " ! " << cell;
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#endif
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cell->set_marked(true);
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cell->visit_children(*this);
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}
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};
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void Heap::mark_live_cells(const HashTable<Cell*>& roots)
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{
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#ifdef HEAP_DEBUG
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dbg() << "mark_live_cells:";
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#endif
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MarkingVisitor visitor;
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for (auto* root : roots)
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visitor.visit(root);
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}
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void Heap::sweep_dead_cells()
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{
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#ifdef HEAP_DEBUG
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dbg() << "sweep_dead_cells:";
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#endif
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for (auto& block : m_blocks) {
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block->for_each_cell([&](Cell* cell) {
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if (cell->is_live()) {
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if (!cell->is_marked()) {
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#ifdef HEAP_DEBUG
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dbg() << " ~ " << cell;
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#endif
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block->deallocate(cell);
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} else {
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cell->set_marked(false);
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}
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}
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});
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}
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}
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}
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