100 lines
1.8 KiB
C++
100 lines
1.8 KiB
C++
// SPDX-License-Identifier: BSD-2-Clause
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// author: Max Kellermann <max.kellermann@gmail.com>
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#include "HugeAllocator.hxx"
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#include "system/VmaName.hxx"
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#include <new>
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#ifdef __linux__
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#include <sys/mman.h>
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#include <unistd.h>
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#else
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#include <stdlib.h>
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#endif
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#ifdef __linux__
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/**
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* Round up the parameter, make it page-aligned.
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*/
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[[gnu::const]]
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static size_t
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AlignToPageSize(size_t size) noexcept
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{
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static const long page_size = sysconf(_SC_PAGESIZE);
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if (page_size <= 0)
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return size;
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size_t ps(page_size);
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return (size + ps - 1) / ps * ps;
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}
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std::span<std::byte>
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HugeAllocate(size_t size)
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{
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size = AlignToPageSize(size);
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constexpr int flags = MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE;
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void *p = mmap(nullptr, size,
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PROT_READ|PROT_WRITE, flags,
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-1, 0);
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if (p == (void *)-1)
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throw std::bad_alloc();
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#ifdef MADV_HUGEPAGE
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/* allow the Linux kernel to use "Huge Pages", which reduces page
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table overhead for this big chunk of data */
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madvise(p, size, MADV_HUGEPAGE);
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#endif
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return {(std::byte *)p, size};
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}
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void
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HugeFree(void *p, size_t size) noexcept
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{
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munmap(p, AlignToPageSize(size));
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}
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void
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HugeSetName(void *p, size_t size, const char *name) noexcept
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{
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SetVmaName(p, size, name);
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}
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void
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HugeForkCow(void *p, size_t size, bool enable) noexcept
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{
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#ifdef MADV_DONTFORK
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madvise(p, AlignToPageSize(size),
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enable ? MADV_DOFORK : MADV_DONTFORK);
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#endif
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}
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void
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HugeDiscard(void *p, size_t size) noexcept
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{
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#ifdef MADV_DONTNEED
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madvise(p, AlignToPageSize(size), MADV_DONTNEED);
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#endif
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}
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#elif defined(_WIN32)
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std::span<std::byte>
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HugeAllocate(size_t size)
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{
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// TODO: use MEM_LARGE_PAGES
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void *p = VirtualAlloc(nullptr, size,
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MEM_COMMIT|MEM_RESERVE,
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PAGE_READWRITE);
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if (p == nullptr)
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throw std::bad_alloc();
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// TODO: round size up to the page size
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return {(std::byte *)p, size};
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}
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#endif
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