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mimalloc/src/os.c

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/* ----------------------------------------------------------------------------
Copyright (c) 2018, Microsoft Research, Daan Leijen
This is free software; you can redistribute it and/or modify it under the
terms of the MIT license. A copy of the license can be found in the file
"LICENSE" at the root of this distribution.
-----------------------------------------------------------------------------*/
#ifndef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE // ensure mmap flags are defined
#endif
#include "mimalloc.h"
#include "mimalloc-internal.h"
#include "mimalloc-atomic.h"
#include <string.h> // strerror
#include <errno.h>
#if defined(_WIN32)
#include <windows.h>
#elif defined(__wasi__)
// stdlib.h is all we need, and has already been included in mimalloc.h
#else
#include <sys/mman.h> // mmap
#include <unistd.h> // sysconf
#if defined(__linux__)
#include <linux/mman.h> // linux mmap flags
#endif
#if defined(__APPLE__)
#include <mach/vm_statistics.h>
#endif
#endif
/* -----------------------------------------------------------
Initialization.
On windows initializes support for aligned allocation and
large OS pages (if MIMALLOC_LARGE_OS_PAGES is true).
----------------------------------------------------------- */
bool _mi_os_decommit(void* addr, size_t size, mi_stats_t* stats);
bool _mi_os_is_huge_reserved(void* p);
void* _mi_os_try_alloc_from_huge_reserved(size_t size, size_t try_alignment);
static void* mi_align_up_ptr(void* p, size_t alignment) {
return (void*)_mi_align_up((uintptr_t)p, alignment);
}
static uintptr_t _mi_align_down(uintptr_t sz, size_t alignment) {
return (sz / alignment) * alignment;
}
static void* mi_align_down_ptr(void* p, size_t alignment) {
return (void*)_mi_align_down((uintptr_t)p, alignment);
}
// page size (initialized properly in `os_init`)
static size_t os_page_size = 4096;
// minimal allocation granularity
static size_t os_alloc_granularity = 4096;
// if non-zero, use large page allocation
static size_t large_os_page_size = 0;
// OS (small) page size
size_t _mi_os_page_size() {
return os_page_size;
}
// if large OS pages are supported (2 or 4MiB), then return the size, otherwise return the small page size (4KiB)
size_t _mi_os_large_page_size() {
return (large_os_page_size != 0 ? large_os_page_size : _mi_os_page_size());
}
static bool use_large_os_page(size_t size, size_t alignment) {
// if we have access, check the size and alignment requirements
if (large_os_page_size == 0 || !mi_option_is_enabled(mi_option_large_os_pages)) return false;
return ((size % large_os_page_size) == 0 && (alignment % large_os_page_size) == 0);
}
// round to a good allocation size
static size_t mi_os_good_alloc_size(size_t size, size_t alignment) {
UNUSED(alignment);
if (size >= (SIZE_MAX - os_alloc_granularity)) return size; // possible overflow?
return _mi_align_up(size, os_alloc_granularity);
}
#if defined(_WIN32)
// We use VirtualAlloc2 for aligned allocation, but it is only supported on Windows 10 and Windows Server 2016.
// So, we need to look it up dynamically to run on older systems. (use __stdcall for 32-bit compatibility)
// NtAllocateVirtualAllocEx is used for huge OS page allocation (1GiB)
// We hide MEM_EXTENDED_PARAMETER to compile with older SDK's.
#include <winternl.h>
typedef PVOID (__stdcall *PVirtualAlloc2)(HANDLE, PVOID, SIZE_T, ULONG, ULONG, /* MEM_EXTENDED_PARAMETER* */ void*, ULONG);
typedef NTSTATUS (__stdcall *PNtAllocateVirtualMemoryEx)(HANDLE, PVOID*, SIZE_T*, ULONG, ULONG, /* MEM_EXTENDED_PARAMETER* */ PVOID, ULONG);
static PVirtualAlloc2 pVirtualAlloc2 = NULL;
static PNtAllocateVirtualMemoryEx pNtAllocateVirtualMemoryEx = NULL;
void _mi_os_init(void) {
// get the page size
SYSTEM_INFO si;
GetSystemInfo(&si);
if (si.dwPageSize > 0) os_page_size = si.dwPageSize;
if (si.dwAllocationGranularity > 0) os_alloc_granularity = si.dwAllocationGranularity;
// get the VirtualAlloc2 function
HINSTANCE hDll;
hDll = LoadLibrary(TEXT("kernelbase.dll"));
if (hDll != NULL) {
// use VirtualAlloc2FromApp if possible as it is available to Windows store apps
pVirtualAlloc2 = (PVirtualAlloc2)GetProcAddress(hDll, "VirtualAlloc2FromApp");
if (pVirtualAlloc2==NULL) pVirtualAlloc2 = (PVirtualAlloc2)GetProcAddress(hDll, "VirtualAlloc2");
FreeLibrary(hDll);
}
hDll = LoadLibrary(TEXT("ntdll.dll"));
if (hDll != NULL) {
pNtAllocateVirtualMemoryEx = (PNtAllocateVirtualMemoryEx)GetProcAddress(hDll, "NtAllocateVirtualMemoryEx");
FreeLibrary(hDll);
}
// Try to see if large OS pages are supported
unsigned long err = 0;
bool ok = mi_option_is_enabled(mi_option_large_os_pages) || mi_option_is_enabled(mi_option_reserve_huge_os_pages);
if (ok) {
// To use large pages on Windows, we first need access permission
// Set "Lock pages in memory" permission in the group policy editor
// <https://devblogs.microsoft.com/oldnewthing/20110128-00/?p=11643>
HANDLE token = NULL;
ok = OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &token);
if (ok) {
TOKEN_PRIVILEGES tp;
ok = LookupPrivilegeValue(NULL, TEXT("SeLockMemoryPrivilege"), &tp.Privileges[0].Luid);
if (ok) {
tp.PrivilegeCount = 1;
tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
ok = AdjustTokenPrivileges(token, FALSE, &tp, 0, (PTOKEN_PRIVILEGES)NULL, 0);
if (ok) {
err = GetLastError();
ok = (err == ERROR_SUCCESS);
if (ok) {
large_os_page_size = GetLargePageMinimum();
}
}
}
CloseHandle(token);
}
if (!ok) {
if (err == 0) err = GetLastError();
_mi_warning_message("cannot enable large OS page support, error %lu\n", err);
}
}
}
#elif defined(__wasi__)
void _mi_os_init() {
os_page_size = 0x10000; // WebAssembly has a fixed page size: 64KB
os_alloc_granularity = 16;
}
#else
void _mi_os_init() {
// get the page size
long result = sysconf(_SC_PAGESIZE);
if (result > 0) {
os_page_size = (size_t)result;
os_alloc_granularity = os_page_size;
}
if (mi_option_is_enabled(mi_option_large_os_pages)) {
large_os_page_size = (1UL << 21); // 2MiB
}
}
#endif
/* -----------------------------------------------------------
Raw allocation on Windows (VirtualAlloc) and Unix's (mmap).
----------------------------------------------------------- */
static bool mi_os_mem_free(void* addr, size_t size, bool was_committed, mi_stats_t* stats)
{
if (addr == NULL || size == 0 || _mi_os_is_huge_reserved(addr)) return true;
bool err = false;
#if defined(_WIN32)
err = (VirtualFree(addr, 0, MEM_RELEASE) == 0);
#elif defined(__wasi__)
err = 0; // WebAssembly's heap cannot be shrunk
#else
err = (munmap(addr, size) == -1);
#endif
if (was_committed) _mi_stat_decrease(&stats->committed, size);
_mi_stat_decrease(&stats->reserved, size);
if (err) {
#pragma warning(suppress:4996)
_mi_warning_message("munmap failed: %s, addr 0x%8li, size %lu\n", strerror(errno), (size_t)addr, size);
return false;
}
else {
return true;
}
}
#ifdef _WIN32
static void* mi_win_virtual_allocx(void* addr, size_t size, size_t try_alignment, DWORD flags) {
#if defined(MEM_EXTENDED_PARAMETER_TYPE_BITS)
// on modern Windows try use NtAllocateVirtualMemoryEx for 1GiB huge pages
if ((size % ((uintptr_t)1 << 30)) == 0 /* 1GiB multiple */
&& (flags & MEM_LARGE_PAGES) != 0 && (flags & MEM_COMMIT) != 0 && (flags & MEM_RESERVE) != 0
&& (addr != NULL || try_alignment == 0 || try_alignment % _mi_os_page_size() == 0)
&& pNtAllocateVirtualMemoryEx != NULL)
{
#ifndef MEM_EXTENDED_PARAMETER_NONPAGED_HUGE
#define MEM_EXTENDED_PARAMETER_NONPAGED_HUGE (0x10)
#endif
MEM_EXTENDED_PARAMETER param = { 0, 0 };
param.Type = 5; // == MemExtendedParameterAttributeFlags;
param.ULong64 = MEM_EXTENDED_PARAMETER_NONPAGED_HUGE;
SIZE_T psize = size;
void* base = addr;
NTSTATUS err = (*pNtAllocateVirtualMemoryEx)(GetCurrentProcess(), &base, &psize, flags, PAGE_READWRITE, &param, 1);
if (err == 0) {
return base;
}
else {
// else fall back to regular large OS pages
_mi_warning_message("unable to allocate huge (1GiB) page, trying large (2MiB) pages instead (error 0x%lx)\n", err);
}
}
#endif
#if (MI_INTPTR_SIZE >= 8)
// on 64-bit systems, use the virtual address area after 4TiB for 4MiB aligned allocations
#define MI_HINT_START ((intptr_t)4 << 40)
static volatile _Atomic(intptr_t) aligned_base = ATOMIC_VAR_INIT(MI_HINT_START); // starting at 4TiB
if (addr == NULL && try_alignment > 0 &&
try_alignment <= MI_SEGMENT_SIZE && (size%MI_SEGMENT_SIZE) == 0)
{
intptr_t hint = mi_atomic_add(&aligned_base, size);
if (hint > ((intptr_t)30<<40)) { // try to wrap around after 30TiB (area after 32TiB is used for huge OS pages)
mi_atomic_cas_strong(mi_atomic_cast(uintptr_t,&aligned_base),MI_HINT_START,hint + size);
}
if (hint%try_alignment == 0) {
return VirtualAlloc((void*)hint, size, flags, PAGE_READWRITE);
}
}
#endif
#if defined(MEM_EXTENDED_PARAMETER_TYPE_BITS)
// on modern Windows try use VirtualAlloc2 for aligned allocation
if (try_alignment > 0 && (try_alignment % _mi_os_page_size()) == 0 && pVirtualAlloc2 != NULL) {
MEM_ADDRESS_REQUIREMENTS reqs = { 0 };
reqs.Alignment = try_alignment;
MEM_EXTENDED_PARAMETER param = { 0 };
param.Type = MemExtendedParameterAddressRequirements;
param.Pointer = &reqs;
return (*pVirtualAlloc2)(GetCurrentProcess(), addr, size, flags, PAGE_READWRITE, &param, 1);
}
#endif
return VirtualAlloc(addr, size, flags, PAGE_READWRITE);
}
static void* mi_win_virtual_alloc(void* addr, size_t size, size_t try_alignment, DWORD flags, bool large_only, bool allow_large, bool* is_large) {
mi_assert_internal(!(large_only && !allow_large));
static volatile _Atomic(uintptr_t) large_page_try_ok; // = 0;
void* p = NULL;
if ((large_only || use_large_os_page(size, try_alignment))
&& allow_large && (flags&MEM_COMMIT)!=0 && (flags&MEM_RESERVE)!=0) {
uintptr_t try_ok = mi_atomic_read(&large_page_try_ok);
if (!large_only && try_ok > 0) {
// if a large page allocation fails, it seems the calls to VirtualAlloc get very expensive.
// therefore, once a large page allocation failed, we don't try again for `large_page_try_ok` times.
mi_atomic_cas_weak(&large_page_try_ok, try_ok - 1, try_ok);
}
else {
// large OS pages must always reserve and commit.
*is_large = true;
p = mi_win_virtual_allocx(addr, size, try_alignment, flags | MEM_LARGE_PAGES);
if (large_only) return p;
// fall back to non-large page allocation on error (`p == NULL`).
if (p == NULL) {
mi_atomic_write(&large_page_try_ok,10); // on error, don't try again for the next N allocations
}
}
}
if (p == NULL) {
*is_large = ((flags&MEM_LARGE_PAGES) != 0);
p = mi_win_virtual_allocx(addr, size, try_alignment, flags);
}
if (p == NULL) {
_mi_warning_message("unable to alloc mem error: err: %i size: 0x%x \n", GetLastError(), size);
}
return p;
}
#elif defined(__wasi__)
static void* mi_wasm_heap_grow(size_t size, size_t try_alignment) {
uintptr_t base = __builtin_wasm_memory_size(0) * _mi_os_page_size();
uintptr_t aligned_base = _mi_align_up(base, (uintptr_t) try_alignment);
size_t alloc_size = _mi_align_up( aligned_base - base + size, _mi_os_page_size());
mi_assert(alloc_size >= size && (alloc_size % _mi_os_page_size()) == 0);
if (alloc_size < size) return NULL;
if (__builtin_wasm_memory_grow(0, alloc_size / _mi_os_page_size()) == SIZE_MAX) {
errno = ENOMEM;
return NULL;
}
return (void*)aligned_base;
}
#else
#define MI_OS_USE_MMAP
static void* mi_unix_mmapx(void* addr, size_t size, size_t try_alignment, int protect_flags, int flags, int fd) {
void* p = NULL;
#if (MI_INTPTR_SIZE >= 8) && !defined(MAP_ALIGNED)
// on 64-bit systems, use the virtual address area after 4TiB for 4MiB aligned allocations
#define MI_HINT_START ((intptr_t)4 << 40)
static volatile _Atomic(intptr_t) aligned_base = ATOMIC_VAR_INIT(MI_HINT_START); // starting at 4TiB
if (addr==NULL && try_alignment <= MI_SEGMENT_SIZE && (size%MI_SEGMENT_SIZE)==0) {
intptr_t hint = mi_atomic_add(&aligned_base,size);
if (hint > ((intptr_t)30<<40)) { // try to wrap around after 30TiB (area after 32TiB is used for huge OS pages)
mi_atomic_cas_strong(mi_atomic_cast(uintptr_t,&aligned_base), MI_HINT_START, hint + size);
}
if (hint%try_alignment == 0) {
p = mmap((void*)hint,size,protect_flags,flags,fd,0);
if (p==MAP_FAILED) p = NULL; // fall back to regular mmap
}
}
#else
UNUSED(try_alignment);
#endif
if (p==NULL) {
p = mmap(addr,size,protect_flags,flags,fd,0);
if (p==MAP_FAILED) p = NULL;
}
return p;
}
static void* mi_unix_mmap(void* addr, size_t size, size_t try_alignment, int protect_flags, bool large_only, bool allow_large, bool* is_large) {
void* p = NULL;
#if !defined(MAP_ANONYMOUS)
#define MAP_ANONYMOUS MAP_ANON
#endif
int flags = MAP_PRIVATE | MAP_ANONYMOUS;
int fd = -1;
#if defined(MAP_ALIGNED) // BSD
if (try_alignment > 0) {
size_t n = _mi_bsr(try_alignment);
if (((size_t)1 << n) == try_alignment && n >= 12 && n <= 30) { // alignment is a power of 2 and 4096 <= alignment <= 1GiB
flags |= MAP_ALIGNED(n);
}
}
#endif
#if defined(PROT_MAX)
protect_flags |= PROT_MAX(PROT_READ | PROT_WRITE); // BSD
#endif
#if defined(VM_MAKE_TAG)
// macOS: tracking anonymous page with a specific ID. (All up to 98 are taken officially but LLVM sanitizers had taken 99)
int os_tag = (int)mi_option_get(mi_option_os_tag);
if (os_tag < 100 || os_tag > 255) os_tag = 100;
fd = VM_MAKE_TAG(os_tag);
#endif
if ((large_only || use_large_os_page(size, try_alignment)) && allow_large) {
static volatile _Atomic(uintptr_t) large_page_try_ok; // = 0;
uintptr_t try_ok = mi_atomic_read(&large_page_try_ok);
if (!large_only && try_ok > 0) {
// If the OS is not configured for large OS pages, or the user does not have
// enough permission, the `mmap` will always fail (but it might also fail for other reasons).
// Therefore, once a large page allocation failed, we don't try again for `large_page_try_ok` times
// to avoid too many failing calls to mmap.
mi_atomic_cas_weak(&large_page_try_ok, try_ok - 1, try_ok);
}
else {
int lflags = flags;
int lfd = fd;
#ifdef MAP_ALIGNED_SUPER
lflags |= MAP_ALIGNED_SUPER;
#endif
#ifdef MAP_HUGETLB
lflags |= MAP_HUGETLB;
#endif
#ifdef MAP_HUGE_1GB
if ((size % ((uintptr_t)1 << 30)) == 0) {
lflags |= MAP_HUGE_1GB;
}
else
#endif
{
#ifdef MAP_HUGE_2MB
lflags |= MAP_HUGE_2MB;
#endif
}
#ifdef VM_FLAGS_SUPERPAGE_SIZE_2MB
lfd |= VM_FLAGS_SUPERPAGE_SIZE_2MB;
#endif
if (large_only || lflags != flags) {
// try large OS page allocation
*is_large = true;
p = mi_unix_mmapx(addr, size, try_alignment, protect_flags, lflags, lfd);
#ifdef MAP_HUGE_1GB
if (p == NULL && (lflags & MAP_HUGE_1GB) != 0) {
_mi_warning_message("unable to allocate huge (1GiB) page, trying large (2MiB) pages instead (error %i)\n", errno);
lflags = ((lflags & ~MAP_HUGE_1GB) | MAP_HUGE_2MB);
p = mi_unix_mmapx(addr, size, try_alignment, protect_flags, lflags, lfd);
}
#endif
if (large_only) return p;
if (p == NULL) {
mi_atomic_write(&large_page_try_ok, 10); // on error, don't try again for the next N allocations
}
}
}
}
if (p == NULL) {
*is_large = false;
p = mi_unix_mmapx(addr, size, try_alignment, protect_flags, flags, fd);
#if defined(MADV_HUGEPAGE)
// Many Linux systems don't allow MAP_HUGETLB but they support instead
// transparent huge pages (TPH). It is not required to call `madvise` with MADV_HUGE
// though since properly aligned allocations will already use large pages if available
// in that case -- in particular for our large regions (in `memory.c`).
// However, some systems only allow TPH if called with explicit `madvise`, so
// when large OS pages are enabled for mimalloc, we call `madvice` anyways.
if (allow_large && use_large_os_page(size, try_alignment)) {
if (madvise(p, size, MADV_HUGEPAGE) == 0) {
*is_large = true; // possibly
};
}
#endif
}
return p;
}
#endif
// Primitive allocation from the OS.
// Note: the `try_alignment` is just a hint and the returned pointer is not guaranteed to be aligned.
static void* mi_os_mem_alloc(size_t size, size_t try_alignment, bool commit, bool allow_large, bool* is_large, mi_stats_t* stats) {
mi_assert_internal(size > 0 && (size % _mi_os_page_size()) == 0);
if (size == 0) return NULL;
if (!commit) allow_large = false;
void* p = NULL;
if (commit && allow_large) {
p = _mi_os_try_alloc_from_huge_reserved(size, try_alignment);
if (p != NULL) {
*is_large = true;
return p;
}
}
#if defined(_WIN32)
int flags = MEM_RESERVE;
if (commit) flags |= MEM_COMMIT;
p = mi_win_virtual_alloc(NULL, size, try_alignment, flags, false, allow_large, is_large);
#elif defined(__wasi__)
*is_large = false;
p = mi_wasm_heap_grow(size, try_alignment);
#else
int protect_flags = (commit ? (PROT_WRITE | PROT_READ) : PROT_NONE);
p = mi_unix_mmap(NULL, size, try_alignment, protect_flags, false, allow_large, is_large);
#endif
_mi_stat_increase(&stats->mmap_calls, 1);
if (p != NULL) {
_mi_stat_increase(&stats->reserved, size);
if (commit) { _mi_stat_increase(&stats->committed, size); }
}
return p;
}
// Primitive aligned allocation from the OS.
// This function guarantees the allocated memory is aligned.
static void* mi_os_mem_alloc_aligned(size_t size, size_t alignment, bool commit, bool allow_large, bool* is_large, mi_stats_t* stats) {
mi_assert_internal(alignment >= _mi_os_page_size() && ((alignment & (alignment - 1)) == 0));
mi_assert_internal(size > 0 && (size % _mi_os_page_size()) == 0);
if (!commit) allow_large = false;
if (!(alignment >= _mi_os_page_size() && ((alignment & (alignment - 1)) == 0))) return NULL;
size = _mi_align_up(size, _mi_os_page_size());
// try first with a hint (this will be aligned directly on Win 10+ or BSD)
void* p = mi_os_mem_alloc(size, alignment, commit, allow_large, is_large, stats);
if (p == NULL) return NULL;
// if not aligned, free it, overallocate, and unmap around it
if (((uintptr_t)p % alignment != 0)) {
mi_os_mem_free(p, size, commit, stats);
if (size >= (SIZE_MAX - alignment)) return NULL; // overflow
size_t over_size = size + alignment;
#if _WIN32
// over-allocate and than re-allocate exactly at an aligned address in there.
// this may fail due to threads allocating at the same time so we
// retry this at most 3 times before giving up.
// (we can not decommit around the overallocation on Windows, because we can only
// free the original pointer, not one pointing inside the area)
int flags = MEM_RESERVE;
if (commit) flags |= MEM_COMMIT;
for (int tries = 0; tries < 3; tries++) {
// over-allocate to determine a virtual memory range
p = mi_os_mem_alloc(over_size, alignment, commit, false, is_large, stats);
if (p == NULL) return NULL; // error
if (((uintptr_t)p % alignment) == 0) {
// if p happens to be aligned, just decommit the left-over area
_mi_os_decommit((uint8_t*)p + size, over_size - size, stats);
break;
}
else {
// otherwise free and allocate at an aligned address in there
mi_os_mem_free(p, over_size, commit, stats);
void* aligned_p = mi_align_up_ptr(p, alignment);
p = mi_win_virtual_alloc(aligned_p, size, alignment, flags, false, allow_large, is_large);
if (p == aligned_p) break; // success!
if (p != NULL) { // should not happen?
mi_os_mem_free(p, size, commit, stats);
p = NULL;
}
}
}
#else
// overallocate...
p = mi_os_mem_alloc(over_size, alignment, commit, false, is_large, stats);
if (p == NULL) return NULL;
// and selectively unmap parts around the over-allocated area.
void* aligned_p = mi_align_up_ptr(p, alignment);
size_t pre_size = (uint8_t*)aligned_p - (uint8_t*)p;
size_t mid_size = _mi_align_up(size, _mi_os_page_size());
size_t post_size = over_size - pre_size - mid_size;
mi_assert_internal(pre_size < over_size && post_size < over_size && mid_size >= size);
if (pre_size > 0) mi_os_mem_free(p, pre_size, commit, stats);
if (post_size > 0) mi_os_mem_free((uint8_t*)aligned_p + mid_size, post_size, commit, stats);
// we can return the aligned pointer on `mmap` systems
p = aligned_p;
#endif
}
mi_assert_internal(p == NULL || (p != NULL && ((uintptr_t)p % alignment) == 0));
return p;
}
/* -----------------------------------------------------------
OS API: alloc, free, alloc_aligned
----------------------------------------------------------- */
void* _mi_os_alloc(size_t size, mi_stats_t* stats) {
if (size == 0) return NULL;
size = mi_os_good_alloc_size(size, 0);
bool is_large = false;
return mi_os_mem_alloc(size, 0, true, false, &is_large, stats);
}
void _mi_os_free_ex(void* p, size_t size, bool was_committed, mi_stats_t* stats) {
if (size == 0 || p == NULL) return;
size = mi_os_good_alloc_size(size, 0);
mi_os_mem_free(p, size, was_committed, stats);
}
void _mi_os_free(void* p, size_t size, mi_stats_t* stats) {
_mi_os_free_ex(p, size, true, stats);
}
void* _mi_os_alloc_aligned(size_t size, size_t alignment, bool commit, bool* large, mi_os_tld_t* tld)
{
if (size == 0) return NULL;
size = mi_os_good_alloc_size(size, alignment);
alignment = _mi_align_up(alignment, _mi_os_page_size());
bool allow_large = false;
if (large != NULL) {
allow_large = *large;
*large = false;
}
return mi_os_mem_alloc_aligned(size, alignment, commit, allow_large, (large!=NULL?large:&allow_large), tld->stats);
}
/* -----------------------------------------------------------
OS memory API: reset, commit, decommit, protect, unprotect.
----------------------------------------------------------- */
// OS page align within a given area, either conservative (pages inside the area only),
// or not (straddling pages outside the area is possible)
static void* mi_os_page_align_areax(bool conservative, void* addr, size_t size, size_t* newsize) {
mi_assert(addr != NULL && size > 0);
if (newsize != NULL) *newsize = 0;
if (size == 0 || addr == NULL) return NULL;
// page align conservatively within the range
void* start = (conservative ? mi_align_up_ptr(addr, _mi_os_page_size())
: mi_align_down_ptr(addr, _mi_os_page_size()));
void* end = (conservative ? mi_align_down_ptr((uint8_t*)addr + size, _mi_os_page_size())
: mi_align_up_ptr((uint8_t*)addr + size, _mi_os_page_size()));
ptrdiff_t diff = (uint8_t*)end - (uint8_t*)start;
if (diff <= 0) return NULL;
mi_assert_internal((conservative && (size_t)diff <= size) || (!conservative && (size_t)diff >= size));
if (newsize != NULL) *newsize = (size_t)diff;
return start;
}
static void* mi_os_page_align_area_conservative(void* addr, size_t size, size_t* newsize) {
return mi_os_page_align_areax(true, addr, size, newsize);
}
// Commit/Decommit memory.
// Usuelly commit is aligned liberal, while decommit is aligned conservative.
// (but not for the reset version where we want commit to be conservative as well)
static bool mi_os_commitx(void* addr, size_t size, bool commit, bool conservative, bool* is_zero, mi_stats_t* stats) {
// page align in the range, commit liberally, decommit conservative
*is_zero = false;
size_t csize;
void* start = mi_os_page_align_areax(conservative, addr, size, &csize);
if (csize == 0 || _mi_os_is_huge_reserved(addr)) return true;
int err = 0;
if (commit) {
_mi_stat_increase(&stats->committed, csize);
_mi_stat_increase(&stats->commit_calls, 1);
}
else {
_mi_stat_decrease(&stats->committed, csize);
}
#if defined(_WIN32)
if (commit) {
// if the memory was already committed, the call succeeds but it is not zero'd
// *is_zero = true;
void* p = VirtualAlloc(start, csize, MEM_COMMIT, PAGE_READWRITE);
err = (p == start ? 0 : GetLastError());
}
else {
BOOL ok = VirtualFree(start, csize, MEM_DECOMMIT);
err = (ok ? 0 : GetLastError());
}
#elif defined(__wasi__)
// WebAssembly guests can't control memory protection
#else
err = mprotect(start, csize, (commit ? (PROT_READ | PROT_WRITE) : PROT_NONE));
#endif
if (err != 0) {
_mi_warning_message("commit/decommit error: start: 0x%p, csize: 0x%x, err: %i\n", start, csize, err);
}
mi_assert_internal(err == 0);
return (err == 0);
}
bool _mi_os_commit(void* addr, size_t size, bool* is_zero, mi_stats_t* stats) {
return mi_os_commitx(addr, size, true, false /* conservative? */, is_zero, stats);
}
bool _mi_os_decommit(void* addr, size_t size, mi_stats_t* stats) {
bool is_zero;
return mi_os_commitx(addr, size, false, true /* conservative? */, &is_zero, stats);
}
bool _mi_os_commit_unreset(void* addr, size_t size, bool* is_zero, mi_stats_t* stats) {
return mi_os_commitx(addr, size, true, true /* conservative? */, is_zero, stats);
}
// Signal to the OS that the address range is no longer in use
// but may be used later again. This will release physical memory
// pages and reduce swapping while keeping the memory committed.
// We page align to a conservative area inside the range to reset.
static bool mi_os_resetx(void* addr, size_t size, bool reset, mi_stats_t* stats) {
// page align conservatively within the range
size_t csize;
void* start = mi_os_page_align_area_conservative(addr, size, &csize);
if (csize == 0 || _mi_os_is_huge_reserved(addr)) return true;
if (reset) _mi_stat_increase(&stats->reset, csize);
else _mi_stat_decrease(&stats->reset, csize);
if (!reset) return true; // nothing to do on unreset!
#if (MI_DEBUG>1)
if (!mi_option_is_enabled(mi_option_secure)) {
memset(start, 0, csize); // pretend it is eagerly reset
}
#endif
#if defined(_WIN32)
// Testing shows that for us (on `malloc-large`) MEM_RESET is 2x faster than DiscardVirtualMemory
void* p = VirtualAlloc(start, csize, MEM_RESET, PAGE_READWRITE);
mi_assert_internal(p == start);
#if 1
if (p == start) {
VirtualUnlock(start,csize); // VirtualUnlock after MEM_RESET removes the memory from the working set
}
#endif
if (p != start) return false;
#else
#if defined(MADV_FREE)
static int advice = MADV_FREE;
int err = madvise(start, csize, advice);
if (err != 0 && errno == EINVAL && advice == MADV_FREE) {
// if MADV_FREE is not supported, fall back to MADV_DONTNEED from now on
advice = MADV_DONTNEED;
err = madvise(start, csize, advice);
}
#elif defined(__wasi__)
int err = 0;
#else
int err = madvise(start, csize, MADV_DONTNEED);
#endif
if (err != 0) {
_mi_warning_message("madvise reset error: start: 0x%p, csize: 0x%x, errno: %i\n", start, csize, errno);
}
//mi_assert(err == 0);
if (err != 0) return false;
#endif
return true;
}
// Signal to the OS that the address range is no longer in use
// but may be used later again. This will release physical memory
// pages and reduce swapping while keeping the memory committed.
// We page align to a conservative area inside the range to reset.
bool _mi_os_reset(void* addr, size_t size, mi_stats_t* stats) {
if (mi_option_is_enabled(mi_option_reset_decommits)) {
return _mi_os_decommit(addr,size,stats);
}
else {
return mi_os_resetx(addr, size, true, stats);
}
}
bool _mi_os_unreset(void* addr, size_t size, bool* is_zero, mi_stats_t* stats) {
if (mi_option_is_enabled(mi_option_reset_decommits)) {
return _mi_os_commit_unreset(addr, size, is_zero, stats); // re-commit it (conservatively!)
}
else {
*is_zero = false;
return mi_os_resetx(addr, size, false, stats);
}
}
// Protect a region in memory to be not accessible.
static bool mi_os_protectx(void* addr, size_t size, bool protect) {
// page align conservatively within the range
size_t csize = 0;
void* start = mi_os_page_align_area_conservative(addr, size, &csize);
if (csize == 0) return false;
if (_mi_os_is_huge_reserved(addr)) {
_mi_warning_message("cannot mprotect memory allocated in huge OS pages\n");
}
int err = 0;
#ifdef _WIN32
DWORD oldprotect = 0;
BOOL ok = VirtualProtect(start, csize, protect ? PAGE_NOACCESS : PAGE_READWRITE, &oldprotect);
err = (ok ? 0 : GetLastError());
#elif defined(__wasi__)
err = 0;
#else
err = mprotect(start, csize, protect ? PROT_NONE : (PROT_READ | PROT_WRITE));
#endif
if (err != 0) {
_mi_warning_message("mprotect error: start: 0x%p, csize: 0x%x, err: %i\n", start, csize, err);
}
return (err == 0);
}
bool _mi_os_protect(void* addr, size_t size) {
return mi_os_protectx(addr, size, true);
}
bool _mi_os_unprotect(void* addr, size_t size) {
return mi_os_protectx(addr, size, false);
}
bool _mi_os_shrink(void* p, size_t oldsize, size_t newsize, mi_stats_t* stats) {
// page align conservatively within the range
mi_assert_internal(oldsize > newsize && p != NULL);
if (oldsize < newsize || p == NULL) return false;
if (oldsize == newsize) return true;
// oldsize and newsize should be page aligned or we cannot shrink precisely
void* addr = (uint8_t*)p + newsize;
size_t size = 0;
void* start = mi_os_page_align_area_conservative(addr, oldsize - newsize, &size);
if (size == 0 || start != addr) return false;
#ifdef _WIN32
// we cannot shrink on windows, but we can decommit
return _mi_os_decommit(start, size, stats);
#else
return mi_os_mem_free(start, size, true, stats);
#endif
}
/* ----------------------------------------------------------------------------
Support for huge OS pages (1Gib) that are reserved up-front and never
released. Only regions are allocated in here (see `memory.c`) so the memory
will be reused.
-----------------------------------------------------------------------------*/
#define MI_HUGE_OS_PAGE_SIZE ((size_t)1 << 30) // 1GiB
typedef struct mi_huge_info_s {
volatile _Atomic(void*) start; // start of huge page area (32TiB)
volatile _Atomic(size_t) reserved; // total reserved size
volatile _Atomic(size_t) used; // currently allocated
} mi_huge_info_t;
static mi_huge_info_t os_huge_reserved = { NULL, 0, ATOMIC_VAR_INIT(0) };
bool _mi_os_is_huge_reserved(void* p) {
return (mi_atomic_read_ptr(&os_huge_reserved.start) != NULL &&
p >= mi_atomic_read_ptr(&os_huge_reserved.start) &&
(uint8_t*)p < (uint8_t*)mi_atomic_read_ptr(&os_huge_reserved.start) + mi_atomic_read(&os_huge_reserved.reserved));
}
void* _mi_os_try_alloc_from_huge_reserved(size_t size, size_t try_alignment)
{
// only allow large aligned allocations (e.g. regions)
if (size < MI_SEGMENT_SIZE || (size % MI_SEGMENT_SIZE) != 0) return NULL;
if (try_alignment > MI_SEGMENT_SIZE) return NULL;
if (mi_atomic_read_ptr(&os_huge_reserved.start)==NULL) return NULL;
if (mi_atomic_read(&os_huge_reserved.used) >= mi_atomic_read(&os_huge_reserved.reserved)) return NULL; // already full
// always aligned
mi_assert_internal(mi_atomic_read(&os_huge_reserved.used) % MI_SEGMENT_SIZE == 0 );
mi_assert_internal( (uintptr_t)mi_atomic_read_ptr(&os_huge_reserved.start) % MI_SEGMENT_SIZE == 0 );
// try to reserve space
size_t base = mi_atomic_addu( &os_huge_reserved.used, size );
if ((base + size) > os_huge_reserved.reserved) {
// "free" our over-allocation
mi_atomic_subu( &os_huge_reserved.used, size);
return NULL;
}
// success!
uint8_t* p = (uint8_t*)mi_atomic_read_ptr(&os_huge_reserved.start) + base;
mi_assert_internal( (uintptr_t)p % MI_SEGMENT_SIZE == 0 );
return p;
}
/*
static void mi_os_free_huge_reserved() {
uint8_t* addr = os_huge_reserved.start;
size_t total = os_huge_reserved.reserved;
os_huge_reserved.reserved = 0;
os_huge_reserved.start = NULL;
for( size_t current = 0; current < total; current += MI_HUGE_OS_PAGE_SIZE) {
_mi_os_free(addr + current, MI_HUGE_OS_PAGE_SIZE, &_mi_stats_main);
}
}
*/
#if !(MI_INTPTR_SIZE >= 8 && (defined(_WIN32) || defined(MI_OS_USE_MMAP)))
int mi_reserve_huge_os_pages(size_t pages, double max_secs, size_t* pages_reserved) mi_attr_noexcept {
UNUSED(pages); UNUSED(max_secs);
if (pages_reserved != NULL) *pages_reserved = 0;
return ENOMEM;
}
#else
int mi_reserve_huge_os_pages( size_t pages, double max_secs, size_t* pages_reserved ) mi_attr_noexcept
{
if (pages_reserved != NULL) *pages_reserved = 0;
if (max_secs==0) return ETIMEDOUT; // timeout
if (pages==0) return 0; // ok
if (!mi_atomic_cas_ptr_strong(&os_huge_reserved.start,(void*)1,NULL)) return ETIMEDOUT; // already reserved
// Allocate one page at the time but try to place them contiguously
// We allocate one page at the time to be able to abort if it takes too long
double start_t = _mi_clock_start();
uint8_t* start = (uint8_t*)((uintptr_t)32 << 40); // 32TiB virtual start address
uint8_t* addr = start; // current top of the allocations
for (size_t page = 0; page < pages; page++, addr += MI_HUGE_OS_PAGE_SIZE ) {
// allocate a page
void* p = NULL;
bool is_large = true;
#ifdef _WIN32
p = mi_win_virtual_alloc(addr, MI_HUGE_OS_PAGE_SIZE, 0, MEM_LARGE_PAGES | MEM_COMMIT | MEM_RESERVE, true, true, &is_large);
#elif defined(MI_OS_USE_MMAP)
p = mi_unix_mmap(addr, MI_HUGE_OS_PAGE_SIZE, 0, PROT_READ | PROT_WRITE, true, true, &is_large);
#else
// always fail
#endif
// Did we succeed at a contiguous address?
if (p != addr) {
// no success, issue a warning and return with an error
if (p != NULL) {
_mi_warning_message("could not allocate contiguous huge page %zu at 0x%p\n", page, addr);
_mi_os_free(p, MI_HUGE_OS_PAGE_SIZE, &_mi_stats_main );
}
else {
#ifdef _WIN32
int err = GetLastError();
#else
int err = errno;
#endif
_mi_warning_message("could not allocate huge page %zu at 0x%p, error: %i\n", page, addr, err);
}
return ENOMEM;
}
// success, record it
if (page==0) {
mi_atomic_write_ptr(&os_huge_reserved.start, addr);
mi_atomic_write(&os_huge_reserved.reserved, MI_HUGE_OS_PAGE_SIZE);
}
else {
mi_atomic_addu(&os_huge_reserved.reserved,MI_HUGE_OS_PAGE_SIZE);
}
_mi_stat_increase(&_mi_stats_main.committed, MI_HUGE_OS_PAGE_SIZE);
_mi_stat_increase(&_mi_stats_main.reserved, MI_HUGE_OS_PAGE_SIZE);
if (pages_reserved != NULL) { *pages_reserved = page + 1; }
// check for timeout
double elapsed = _mi_clock_end(start_t);
if (elapsed > max_secs) return ETIMEDOUT;
if (page >= 1) {
double estimate = ((elapsed / (double)(page+1)) * (double)pages);
if (estimate > 1.5*max_secs) return ETIMEDOUT; // seems like we are going to timeout
}
}
_mi_verbose_message("reserved %zu huge pages\n", pages);
return 0;
}
#endif
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