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LibGC: Use native windows allocation methods for GC blocks

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This allows us to use DiscardVirtualMemory in the same way that we
use madvise with MADV_DONTNEED and MADV_FREE on Unix systems.
This commit is contained in:
R-Goc 2025-05-28 23:57:08 -06:00 • committed by Andrew Kaster
commit d5cb940fe0
Notes: github-actions[bot] 2025-05-29 09:28:03 +00:00
1 changed files with 27 additions and 1 deletions
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28
Libraries/LibGC/BlockAllocator.cpp
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@ -1,9 +1,12 @@
/* /*
* Copyright (c) 2021-2023, Andreas Kling <andreas@ladybird.org> * Copyright (c) 2021-2023, Andreas Kling <andreas@ladybird.org>
* Copyright (c) 2025, Ryszard Goc <ryszardgoc@gmail.com>
* *
* SPDX-License-Identifier: BSD-2-Clause * SPDX-License-Identifier: BSD-2-Clause
*/ */
#include <AK/Assertions.h>
#include <AK/Format.h>
#include <AK/Platform.h> #include <AK/Platform.h>
#include <AK/Random.h> #include <AK/Random.h>
#include <AK/Vector.h> #include <AK/Vector.h>
@ -20,16 +23,28 @@
# define USE_FALLBACK_BLOCK_DEALLOCATION # define USE_FALLBACK_BLOCK_DEALLOCATION
#endif #endif
#if defined(AK_OS_WINDOWS)
# include <AK/Windows.h>
# include <memoryapi.h>
#endif
namespace GC { namespace GC {
BlockAllocator::~BlockAllocator() BlockAllocator::~BlockAllocator()
{ {
for (auto* block : m_blocks) { for (auto* block : m_blocks) {
ASAN_UNPOISON_MEMORY_REGION(block, HeapBlock::block_size); ASAN_UNPOISON_MEMORY_REGION(block, HeapBlock::block_size);
#if !defined(AK_OS_WINDOWS)
if (munmap(block, HeapBlock::block_size) < 0) { if (munmap(block, HeapBlock::block_size) < 0) {
perror("munmap"); perror("munmap");
VERIFY_NOT_REACHED(); VERIFY_NOT_REACHED();
} }
#else
if (!VirtualFree(block, HeapBlock::block_size, MEM_RELEASE)) {
warnln("{}", Error::from_windows_error());
VERIFY_NOT_REACHED();
}
#endif
} }
} }
@ -44,8 +59,13 @@ void* BlockAllocator::allocate_block([[maybe_unused]] char const* name)
return block; return block;
} }
#if !defined(AK_OS_WINDOWS)
auto* block = (HeapBlock*)mmap(nullptr, HeapBlock::block_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); auto* block = (HeapBlock*)mmap(nullptr, HeapBlock::block_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
VERIFY(block != MAP_FAILED); VERIFY(block != MAP_FAILED);
#else
auto* block = (HeapBlock*)VirtualAlloc(NULL, HeapBlock::block_size, MEM_COMMIT, PAGE_READWRITE);
VERIFY(block);
#endif
LSAN_REGISTER_ROOT_REGION(block, HeapBlock::block_size); LSAN_REGISTER_ROOT_REGION(block, HeapBlock::block_size);
return block; return block;
} }
@ -54,7 +74,13 @@ void BlockAllocator::deallocate_block(void* block)
{ {
VERIFY(block); VERIFY(block);
#if defined(USE_FALLBACK_BLOCK_DEALLOCATION) #if defined(AK_OS_WINDOWS)
DWORD ret = DiscardVirtualMemory(block, HeapBlock::block_size);
if (ret != ERROR_SUCCESS) {
warnln("{}", Error::from_windows_error(ret));
VERIFY_NOT_REACHED();
}
#elif defined(USE_FALLBACK_BLOCK_DEALLOCATION)
// If we can't use any of the nicer techniques, unmap and remap the block to return the physical pages while keeping the VM. // If we can't use any of the nicer techniques, unmap and remap the block to return the physical pages while keeping the VM.
if (munmap(block, HeapBlock::block_size) < 0) { if (munmap(block, HeapBlock::block_size) < 0) {
perror("munmap"); perror("munmap");