e16f2aff6f
This change brings in a new approach to managing address space. It wraps the Pal with a power of two reservation system, that guarantees all returned blocks are naturally aligned to their size. It either lets the Pal perform aligned requests, or over allocates and splits into power of two blocks.
55 lines
1.3 KiB
C++
55 lines
1.3 KiB
C++
#pragma once
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#include "pal_bsd.h"
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namespace snmalloc
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{
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/**
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* FreeBSD-specific platform abstraction layer.
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*
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* This adds aligned allocation using `MAP_ALIGNED` to the generic BSD
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* implementation. This flag is supported by NetBSD and FreeBSD.
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*/
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template<class OS>
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class PALBSD_Aligned : public PALBSD<OS>
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{
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public:
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/**
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* Bitmap of PalFeatures flags indicating the optional features that this
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* PAL supports.
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*
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* This class adds support for aligned allocation.
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*/
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static constexpr uint64_t pal_features =
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AlignedAllocation | PALBSD<OS>::pal_features;
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static constexpr size_t minimum_alloc_size = 4096;
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/**
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* Reserve memory at a specific alignment.
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*/
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template<bool committed>
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void* reserve_aligned(size_t size) noexcept
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{
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// Alignment must be a power of 2.
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SNMALLOC_ASSERT(size == bits::next_pow2(size));
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SNMALLOC_ASSERT(size >= minimum_alloc_size);
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size_t log2align = bits::next_pow2_bits(size);
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void* p = mmap(
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nullptr,
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size,
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PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS | MAP_ALIGNED(log2align),
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-1,
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0);
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if (p == MAP_FAILED)
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PALBSD<OS>::error("Out of memory");
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return p;
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}
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};
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} // namespace snmalloc
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