mirror of
https://github.com/RGBCube/serenity
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c2d9cd8d53
HeapBlock now implements the same lazy freelist as LibC malloc() does, where new blocks start out in a "bump allocator" mode that gets used until we've bump-allocated all the way to the end of the block. Then we fall back to the old freelist style as before. This means we don't have to pre-initialize the freelist on HeapBlock construction. This defers page faults and reduces memory usage for blocks where all cells don't get used. :^)
59 lines
1.5 KiB
C++
59 lines
1.5 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Assertions.h>
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#include <AK/NonnullOwnPtr.h>
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#include <LibJS/Heap/HeapBlock.h>
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#include <stdio.h>
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#include <sys/mman.h>
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namespace JS {
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NonnullOwnPtr<HeapBlock> HeapBlock::create_with_cell_size(Heap& heap, size_t cell_size)
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{
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char name[64];
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snprintf(name, sizeof(name), "LibJS: HeapBlock(%zu)", cell_size);
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#ifdef __serenity__
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auto* block = (HeapBlock*)serenity_mmap(nullptr, block_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_RANDOMIZED | MAP_PRIVATE, 0, 0, block_size, name);
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#else
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auto* block = (HeapBlock*)aligned_alloc(block_size, block_size);
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#endif
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VERIFY(block != MAP_FAILED);
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new (block) HeapBlock(heap, cell_size);
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return NonnullOwnPtr<HeapBlock>(NonnullOwnPtr<HeapBlock>::Adopt, *block);
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}
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void HeapBlock::operator delete(void* ptr)
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{
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#ifdef __serenity__
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int rc = munmap(ptr, block_size);
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VERIFY(rc == 0);
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#else
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free(ptr);
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#endif
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}
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HeapBlock::HeapBlock(Heap& heap, size_t cell_size)
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: m_heap(heap)
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, m_cell_size(cell_size)
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{
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VERIFY(cell_size >= sizeof(FreelistEntry));
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}
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void HeapBlock::deallocate(Cell* cell)
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{
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VERIFY(is_valid_cell_pointer(cell));
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VERIFY(!m_freelist || is_valid_cell_pointer(m_freelist));
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VERIFY(cell->is_live());
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VERIFY(!cell->is_marked());
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cell->~Cell();
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auto* freelist_entry = new (cell) FreelistEntry();
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freelist_entry->set_live(false);
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freelist_entry->next = m_freelist;
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m_freelist = freelist_entry;
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}
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}
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