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improve aligned allocation performance

This commit is contained in:
daan 2021-12-17 13:18:05 -08:00
parent 684c2c82a7
commit 89f583a69b
5 changed files with 108 additions and 43 deletions
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5
include/mimalloc-internal.h
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@ -247,11 +247,6 @@ static inline size_t _mi_wsize_from_size(size_t size) {
return (size + sizeof(uintptr_t) - 1) / sizeof(uintptr_t);
}
// Does malloc satisfy the alignment constraints already?
static inline bool mi_malloc_satisfies_alignment(size_t alignment, size_t size) {
return (alignment == sizeof(void*) || (alignment == MI_MAX_ALIGN_SIZE && size > (MI_MAX_ALIGN_SIZE/2)));
}
// Overflow detecting multiply
#if __has_builtin(__builtin_umul_overflow) || (defined(__GNUC__) && (__GNUC__ >= 5))
#include <limits.h> // UINT_MAX, ULONG_MAX

111
src/alloc-aligned.c
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@ -14,32 +14,14 @@ terms of the MIT license. A copy of the license can be found in the file
// Aligned Allocation
// ------------------------------------------------------
static void* mi_heap_malloc_zero_aligned_at(mi_heap_t* const heap, const size_t size, const size_t alignment, const size_t offset, const bool zero) mi_attr_noexcept {
// note: we don't require `size > offset`, we just guarantee that
// the address at offset is aligned regardless of the allocated size.
mi_assert(alignment > 0);
if (mi_unlikely(size > PTRDIFF_MAX)) return NULL; // we don't allocate more than PTRDIFF_MAX (see <https://sourceware.org/ml/libc-announce/2019/msg00001.html>)
if (mi_unlikely(alignment==0 || !_mi_is_power_of_two(alignment))) return NULL; // require power-of-two (see <https://en.cppreference.com/w/c/memory/aligned_alloc>)
if (mi_unlikely(alignment>MI_ALIGNED_MAX)) return NULL; // we cannot align at a boundary larger than this (or otherwise we cannot find segment headers)
// Fallback primitive aligned allocation -- split out for better codegen
static mi_decl_noinline void* mi_heap_malloc_zero_aligned_at_fallback(mi_heap_t* const heap, const size_t size, const size_t alignment, const size_t offset, const bool zero) mi_attr_noexcept
{
mi_assert_internal(size <= PTRDIFF_MAX);
mi_assert_internal(alignment!=0 && _mi_is_power_of_two(alignment) && alignment <= MI_ALIGNED_MAX);
const uintptr_t align_mask = alignment-1; // for any x, `(x & align_mask) == (x % alignment)`
// try if there is a small block available with just the right alignment
const size_t padsize = size + MI_PADDING_SIZE;
if (mi_likely(padsize <= MI_SMALL_SIZE_MAX)) {
mi_page_t* page = _mi_heap_get_free_small_page(heap,padsize);
const bool is_aligned = (((uintptr_t)page->free+offset) & align_mask)==0;
if (mi_likely(page->free != NULL && is_aligned))
{
#if MI_STAT>1
mi_heap_stat_increase( heap, malloc, size);
#endif
void* p = _mi_page_malloc(heap,page,padsize); // TODO: inline _mi_page_malloc
mi_assert_internal(p != NULL);
mi_assert_internal(((uintptr_t)p + offset) % alignment == 0);
if (zero) _mi_block_zero_init(page,p,size);
return p;
}
}
// use regular allocation if it is guaranteed to fit the alignment constraints
if (offset==0 && alignment<=padsize && padsize<=MI_MEDIUM_OBJ_SIZE_MAX && (padsize&align_mask)==0) {
@ -47,7 +29,7 @@ static void* mi_heap_malloc_zero_aligned_at(mi_heap_t* const heap, const size_t
mi_assert_internal(p == NULL || ((uintptr_t)p % alignment) == 0);
return p;
}
// otherwise over-allocate
void* p = _mi_heap_malloc_zero(heap, size + alignment - 1, zero);
if (p == NULL) return NULL;
@ -56,21 +38,90 @@ static void* mi_heap_malloc_zero_aligned_at(mi_heap_t* const heap, const size_t
uintptr_t adjust = alignment - (((uintptr_t)p + offset) & align_mask);
mi_assert_internal(adjust <= alignment);
void* aligned_p = (adjust == alignment ? p : (void*)((uintptr_t)p + adjust));
if (aligned_p != p) mi_page_set_has_aligned(_mi_ptr_page(p), true);
if (aligned_p != p) mi_page_set_has_aligned(_mi_ptr_page(p), true);
mi_assert_internal(((uintptr_t)aligned_p + offset) % alignment == 0);
mi_assert_internal( p == _mi_page_ptr_unalign(_mi_ptr_segment(aligned_p),_mi_ptr_page(aligned_p),aligned_p) );
mi_assert_internal(p == _mi_page_ptr_unalign(_mi_ptr_segment(aligned_p), _mi_ptr_page(aligned_p), aligned_p));
return aligned_p;
}
// Primitive aligned allocation
static void* mi_heap_malloc_zero_aligned_at(mi_heap_t* const heap, const size_t size, const size_t alignment, const size_t offset, const bool zero) mi_attr_noexcept
{
// note: we don't require `size > offset`, we just guarantee that the address at offset is aligned regardless of the allocated size.
mi_assert(alignment > 0);
if (mi_unlikely(alignment==0 || !_mi_is_power_of_two(alignment))) { // require power-of-two (see <https://en.cppreference.com/w/c/memory/aligned_alloc>)
#if MI_DEBUG > 0
_mi_error_message(EOVERFLOW, "aligned allocation requires the alignment to be a power-of-two (size %zu, alignment %zu)", size, alignment);
#endif
return NULL;
}
if (mi_unlikely(alignment > MI_ALIGNED_MAX)) { // we cannot align at a boundary larger than this (or otherwise we cannot find segment headers)
#if MI_DEBUG > 0
_mi_error_message(EOVERFLOW, "aligned allocation has a maximum alignment of %zu (size %zu, alignment %zu)", MI_ALIGNED_MAX, size, alignment);
#endif
return NULL;
}
if (mi_unlikely(size > PTRDIFF_MAX)) { // we don't allocate more than PTRDIFF_MAX (see <https://sourceware.org/ml/libc-announce/2019/msg00001.html>)
#if MI_DEBUG > 0
_mi_error_message(EOVERFLOW, "aligned allocation request is too large (size %zu, alignment %zu)", size, alignment);
#endif
return NULL;
}
const uintptr_t align_mask = alignment-1; // for any x, `(x & align_mask) == (x % alignment)`
const size_t padsize = size + MI_PADDING_SIZE; // note: cannot overflow due to earlier size > PTRDIFF_MAX check
// try first if there happens to be a small block available with just the right alignment
if (mi_likely(padsize <= MI_SMALL_SIZE_MAX)) {
mi_page_t* page = _mi_heap_get_free_small_page(heap, padsize);
const bool is_aligned = (((uintptr_t)page->free+offset) & align_mask)==0;
if (mi_likely(page->free != NULL && is_aligned))
{
#if MI_STAT>1
mi_heap_stat_increase(heap, malloc, size);
#endif
void* p = _mi_page_malloc(heap, page, padsize); // TODO: inline _mi_page_malloc
mi_assert_internal(p != NULL);
mi_assert_internal(((uintptr_t)p + offset) % alignment == 0);
if (zero) { _mi_block_zero_init(page, p, size); }
return p;
}
}
// fallback
return mi_heap_malloc_zero_aligned_at_fallback(heap, size, alignment, offset, zero);
}
// ------------------------------------------------------
// Optimized mi_heap_malloc_aligned / mi_malloc_aligned
// ------------------------------------------------------
mi_decl_restrict void* mi_heap_malloc_aligned_at(mi_heap_t* heap, size_t size, size_t alignment, size_t offset) mi_attr_noexcept {
return mi_heap_malloc_zero_aligned_at(heap, size, alignment, offset, false);
}
mi_decl_restrict void* mi_heap_malloc_aligned(mi_heap_t* heap, size_t size, size_t alignment) mi_attr_noexcept {
return mi_heap_malloc_aligned_at(heap, size, alignment, 0);
#if !MI_PADDING
// without padding, any small sized allocation is naturally aligned (see also `_mi_segment_page_start`)
if (!_mi_is_power_of_two(alignment)) return NULL;
if (mi_likely(_mi_is_power_of_two(size) && size >= alignment && size <= MI_SMALL_SIZE_MAX))
#else
// with padding, we can only guarantee this for fixed alignments
if (mi_likely((alignment == sizeof(void*) || (alignment == MI_MAX_ALIGN_SIZE && size > (MI_MAX_ALIGN_SIZE/2)))
&& size <= MI_SMALL_SIZE_MAX))
#endif
{
// fast path for common alignment and size
return mi_heap_malloc_small(heap, size);
}
else {
return mi_heap_malloc_aligned_at(heap, size, alignment, 0);
}
}
// ------------------------------------------------------
// Aligned Allocation
// ------------------------------------------------------
mi_decl_restrict void* mi_heap_zalloc_aligned_at(mi_heap_t* heap, size_t size, size_t alignment, size_t offset) mi_attr_noexcept {
return mi_heap_malloc_zero_aligned_at(heap, size, alignment, offset, true);
}
@ -114,6 +165,10 @@ mi_decl_restrict void* mi_calloc_aligned(size_t count, size_t size, size_t align
}
// ------------------------------------------------------
// Aligned re-allocation
// ------------------------------------------------------
static void* mi_heap_realloc_zero_aligned_at(mi_heap_t* heap, void* p, size_t newsize, size_t alignment, size_t offset, bool zero) mi_attr_noexcept {
mi_assert(alignment > 0);
if (alignment <= sizeof(uintptr_t)) return _mi_heap_realloc_zero(heap,p,newsize,zero);

19
src/alloc-posix.c
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@ -56,9 +56,9 @@ int mi_posix_memalign(void** p, size_t alignment, size_t size) mi_attr_noexcept
// Note: The spec dictates we should not modify `*p` on an error. (issue#27)
// <http://man7.org/linux/man-pages/man3/posix_memalign.3.html>
if (p == NULL) return EINVAL;
if (alignment % sizeof(void*) != 0) return EINVAL; // natural alignment
if (!_mi_is_power_of_two(alignment)) return EINVAL; // not a power of 2
void* q = (mi_malloc_satisfies_alignment(alignment, size) ? mi_malloc(size) : mi_malloc_aligned(size, alignment));
if (alignment % sizeof(void*) != 0) return EINVAL; // natural alignment
if (alignment==0 || !_mi_is_power_of_two(alignment)) return EINVAL; // not a power of 2
void* q = mi_malloc_aligned(size, alignment);
if (q==NULL && size != 0) return ENOMEM;
mi_assert_internal(((uintptr_t)q % alignment) == 0);
*p = q;
@ -66,7 +66,7 @@ int mi_posix_memalign(void** p, size_t alignment, size_t size) mi_attr_noexcept
}
mi_decl_restrict void* mi_memalign(size_t alignment, size_t size) mi_attr_noexcept {
void* p = (mi_malloc_satisfies_alignment(alignment,size) ? mi_malloc(size) : mi_malloc_aligned(size, alignment));
void* p = mi_malloc_aligned(size, alignment);
mi_assert_internal(((uintptr_t)p % alignment) == 0);
return p;
}
@ -83,9 +83,14 @@ mi_decl_restrict void* mi_pvalloc(size_t size) mi_attr_noexcept {
}
mi_decl_restrict void* mi_aligned_alloc(size_t alignment, size_t size) mi_attr_noexcept {
if (alignment==0 || !_mi_is_power_of_two(alignment)) return NULL;
if ((size&(alignment-1)) != 0) return NULL; // C11 requires integral multiple, see <https://en.cppreference.com/w/c/memory/aligned_alloc>
void* p = (mi_malloc_satisfies_alignment(alignment, size) ? mi_malloc(size) : mi_malloc_aligned(size, alignment));
if (mi_unlikely((size&(alignment-1)) != 0)) { // C11 requires alignment>0 && integral multiple, see <https://en.cppreference.com/w/c/memory/aligned_alloc>
#if MI_DEBUG > 0
_mi_error_message(EOVERFLOW, "(mi_)aligned_alloc requires the size to be an integral multiple of the alignment (size %zu, alignment %zu)", size, alignment);
#endif
return NULL;
}
// C11 also requires alignment to be a power-of-two which is checked in mi_malloc_aligned
void* p = mi_malloc_aligned(size, alignment);
mi_assert_internal(((uintptr_t)p % alignment) == 0);
return p;
}

2
test/main-override-static.c
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@ -42,7 +42,7 @@ int main() {
free(p1);
free(p2);
free(s);
/* now test if override worked by allocating/freeing across the api's*/
//p1 = mi_malloc(32);
//free(p1);

14
test/test-api.c
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@ -158,6 +158,16 @@ int main(void) {
CHECK_BODY("malloc-aligned5", {
void* p = mi_malloc_aligned(4097,4096); size_t usable = mi_usable_size(p); result = usable >= 4097 && usable < 10000; mi_free(p);
});
CHECK_BODY("malloc-aligned6", {
void* p;
bool ok = true;
for (int i = 1; i < 8 && ok; i++) {
size_t align = 1UL << i;
p = mi_malloc_aligned(2*align, align);
ok = (p != NULL && (uintptr_t)(p) % align == 0); mi_free(p);
}
result = ok;
});
CHECK_BODY("malloc-aligned-at1", {
void* p = mi_malloc_aligned_at(48,32,0); result = (p != NULL && ((uintptr_t)(p) + 0) % 32 == 0); mi_free(p);
});
@ -172,8 +182,8 @@ int main(void) {
ok = (p != NULL && (uintptr_t)(p) % 16 == 0); mi_free(p);
}
result = ok;
});
});
// ---------------------------------------------------
// Heaps
// ---------------------------------------------------