mirror of
https://github.com/SerenityOS/serenity
synced 2026-05-13 18:37:37 +02:00
0e13e00d6a
Before this change, we were hard-coding 4 KiB. This meant that systems with a 16 KiB native page size were wasting 12 KiB per HeapBlock on nothing, leading to worse locality and more mmap/madvise churn. We now query the system page size on startup and use that as the HeapBlock size. The only downside here is that some of the pointer math for finding the base of a HeapBlock now has to use a runtime computed value instead of a compile time constant. But that's a small price to pay for what we get. (cherry picked from commit a6bf253602702c052453d5ccb45a40d8fbb368ba)
96 lines
3.0 KiB
C++
96 lines
3.0 KiB
C++
/*
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* Copyright (c) 2021-2023, 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/Platform.h>
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#include <AK/Random.h>
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#include <AK/Vector.h>
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#include <LibJS/Heap/BlockAllocator.h>
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#include <LibJS/Heap/HeapBlock.h>
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#include <sys/mman.h>
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#ifdef HAS_ADDRESS_SANITIZER
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# include <sanitizer/asan_interface.h>
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# include <sanitizer/lsan_interface.h>
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#endif
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// FIXME: Implement MADV_FREE and/or MADV_DONTNEED on SerenityOS.
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#if defined(AK_OS_SERENITY) || defined(AK_OS_GNU_HURD) || (!defined(MADV_FREE) && !defined(MADV_DONTNEED))
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# define USE_FALLBACK_BLOCK_DEALLOCATION
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#endif
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namespace JS {
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BlockAllocator::~BlockAllocator()
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{
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for (auto* block : m_blocks) {
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ASAN_UNPOISON_MEMORY_REGION(block, HeapBlock::block_size);
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if (munmap(block, HeapBlock::block_size) < 0) {
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perror("munmap");
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VERIFY_NOT_REACHED();
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}
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}
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}
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void* BlockAllocator::allocate_block([[maybe_unused]] char const* name)
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{
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if (!m_blocks.is_empty()) {
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// To reduce predictability, take a random block from the cache.
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size_t random_index = get_random_uniform(m_blocks.size());
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auto* block = m_blocks.unstable_take(random_index);
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ASAN_UNPOISON_MEMORY_REGION(block, HeapBlock::block_size);
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LSAN_REGISTER_ROOT_REGION(block, HeapBlock::block_size);
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#ifdef AK_OS_SERENITY
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if (set_mmap_name(block, HeapBlock::block_size, name) < 0) {
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perror("set_mmap_name");
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VERIFY_NOT_REACHED();
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}
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#endif
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return block;
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}
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#ifdef AK_OS_SERENITY
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auto* block = (HeapBlock*)serenity_mmap(nullptr, HeapBlock::block_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_RANDOMIZED | MAP_PRIVATE, -1, 0, HeapBlock::block_size, name);
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#else
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auto* block = (HeapBlock*)mmap(nullptr, HeapBlock::block_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
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#endif
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VERIFY(block != MAP_FAILED);
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LSAN_REGISTER_ROOT_REGION(block, HeapBlock::block_size);
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return block;
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}
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void BlockAllocator::deallocate_block(void* block)
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{
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VERIFY(block);
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#if defined(USE_FALLBACK_BLOCK_DEALLOCATION)
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// If we can't use any of the nicer techniques, unmap and remap the block to return the physical pages while keeping the VM.
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if (munmap(block, HeapBlock::block_size) < 0) {
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perror("munmap");
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VERIFY_NOT_REACHED();
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}
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if (mmap(block, HeapBlock::block_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0) != block) {
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perror("mmap");
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VERIFY_NOT_REACHED();
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}
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#elif defined(MADV_FREE)
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if (madvise(block, HeapBlock::block_size, MADV_FREE) < 0) {
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perror("madvise(MADV_FREE)");
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VERIFY_NOT_REACHED();
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}
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#elif defined(MADV_DONTNEED)
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if (madvise(block, HeapBlock::block_size, MADV_DONTNEED) < 0) {
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perror("madvise(MADV_DONTNEED)");
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VERIFY_NOT_REACHED();
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}
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#endif
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ASAN_POISON_MEMORY_REGION(block, HeapBlock::block_size);
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LSAN_UNREGISTER_ROOT_REGION(block, HeapBlock::block_size);
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m_blocks.append(block);
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}
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}
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