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Snapshot #11

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38d216e
Snapshot
arnaud-lb Mar 3, 2025
b9df0ca
Implement copy-on-write snapshot
arnaud-lb Mar 12, 2025
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104 changes: 97 additions & 7 deletions Zend/zend_alloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -226,7 +226,6 @@ typedef zend_mm_bitset zend_mm_page_map[ZEND_MM_PAGE_MAP_LEN]; /* 64B */
typedef struct _zend_mm_page zend_mm_page;
typedef struct _zend_mm_bin zend_mm_bin;
typedef struct _zend_mm_free_slot zend_mm_free_slot;
typedef struct _zend_mm_chunk zend_mm_chunk;
typedef struct _zend_mm_huge_list zend_mm_huge_list;

static bool zend_mm_use_huge_pages = false;
Expand Down Expand Up @@ -322,6 +321,9 @@ struct _zend_mm_chunk {
zend_mm_heap heap_slot; /* used only in main chunk */
zend_mm_page_map free_map; /* 512 bits or 64 bytes */
zend_mm_page_info map[ZEND_MM_PAGES]; /* 2 KB = 512 * 4 */
bool preserve; /* Never free this chunk.
Ensures the address space can
not be re-used. */
};

struct _zend_mm_page {
Expand Down Expand Up @@ -804,7 +806,7 @@ static void *zend_mm_chunk_alloc_int(size_t size, size_t alignment)
}
}

static void *zend_mm_chunk_alloc(zend_mm_heap *heap, size_t size, size_t alignment)
ZEND_API void *zend_mm_chunk_alloc(zend_mm_heap *heap, size_t size, size_t alignment)
{
#if ZEND_MM_STORAGE
if (UNEXPECTED(heap->storage)) {
Expand Down Expand Up @@ -1172,11 +1174,15 @@ static zend_always_inline void zend_mm_delete_chunk(zend_mm_heap *heap, zend_mm_
}
}
if (!heap->cached_chunks || chunk->num > heap->cached_chunks->num) {
zend_mm_chunk_free(heap, chunk, ZEND_MM_CHUNK_SIZE);
if (!chunk->preserve) {
zend_mm_chunk_free(heap, chunk, ZEND_MM_CHUNK_SIZE);
}
} else {
//TODO: select the best chunk to delete???
chunk->next = heap->cached_chunks->next;
zend_mm_chunk_free(heap, heap->cached_chunks, ZEND_MM_CHUNK_SIZE);
if (!heap->cached_chunks->preserve) {
zend_mm_chunk_free(heap, heap->cached_chunks, ZEND_MM_CHUNK_SIZE);
}
heap->cached_chunks = chunk;
}
}
Expand Down Expand Up @@ -2195,6 +2201,53 @@ ZEND_API size_t zend_mm_gc(zend_mm_heap *heap)
return collected * ZEND_MM_PAGE_SIZE;
}

ZEND_API zend_mm_chunk *zend_mm_get_chunk_list(zend_mm_heap *heap)
{
return heap->main_chunk;
}

ZEND_API int zend_mm_get_chunks_count(zend_mm_heap *heap)
{
return heap->chunks_count;
}

ZEND_API void *zend_mm_get_huge_list(zend_mm_heap *heap)
{
return heap->huge_list;
}

ZEND_API zend_mm_chunk *zend_mm_get_next_chunk(zend_mm_heap *heap, zend_mm_chunk *chunk)
{
ZEND_ASSERT(chunk->heap == heap);
zend_mm_chunk *next = chunk->next;
if (next == heap->main_chunk) {
return NULL;
}
return next;
}

/* Adds the given chunk to the heap. The chunk is not initialized, and can have
* allocated slots and pages. */
ZEND_API void zend_mm_adopt_chunk(zend_mm_heap *heap, zend_mm_chunk *chunk)
{
/* Do not import free lists, as the chunk may have been created with a
* different key. However, free pages can be allocated. */
chunk->heap = heap;
chunk->next = heap->main_chunk;
chunk->prev = heap->main_chunk->prev;
chunk->prev->next = chunk;
chunk->next->prev = chunk;
chunk->num = chunk->prev->num + 1;
heap->chunks_count++;
heap->peak_chunks_count++;
}

ZEND_API void zend_mm_preserve_chunk(zend_mm_heap *heap, zend_mm_chunk *chunk)
{
ZEND_ASSERT(chunk->heap == heap);
chunk->preserve = true;
}

#if ZEND_DEBUG
/******************/
/* Leak detection */
Expand Down Expand Up @@ -2460,23 +2513,44 @@ ZEND_API void zend_mm_shutdown(zend_mm_heap *heap, bool full, bool silent)
while (heap->cached_chunks) {
p = heap->cached_chunks;
heap->cached_chunks = p->next;
zend_mm_chunk_free(heap, p, ZEND_MM_CHUNK_SIZE);
if (!p->preserve) {
zend_mm_chunk_free(heap, p, ZEND_MM_CHUNK_SIZE);
}
}
/* free the first chunk */
zend_mm_chunk_free(heap, heap->main_chunk, ZEND_MM_CHUNK_SIZE);
if (!heap->main_chunk->preserve) {
zend_mm_chunk_free(heap, heap->main_chunk, ZEND_MM_CHUNK_SIZE);
}
} else {
/* unlink preserved chunks from the cache */
p = heap->cached_chunks;
while (p) {
zend_mm_chunk *q = p->next;
while (q && q->preserve) {
p->next = q = q->next;
heap->cached_chunks_count--;
}
p = q;
}
if (heap->cached_chunks && heap->cached_chunks->preserve) {
heap->cached_chunks_count--;
heap->cached_chunks = heap->cached_chunks->next;
}

/* free some cached chunks to keep average count */
heap->avg_chunks_count = (heap->avg_chunks_count + (double)heap->peak_chunks_count) / 2.0;
while ((double)heap->cached_chunks_count + 0.9 > heap->avg_chunks_count &&
heap->cached_chunks) {
p = heap->cached_chunks;
heap->cached_chunks = p->next;
ZEND_ASSERT(!p->preserve);
zend_mm_chunk_free(heap, p, ZEND_MM_CHUNK_SIZE);
heap->cached_chunks_count--;
}
/* clear cached chunks */
p = heap->cached_chunks;
while (p != NULL) {
ZEND_ASSERT(!p->preserve);
zend_mm_chunk *q = p->next;
memset(p, 0, sizeof(zend_mm_chunk));
p->next = q;
Expand Down Expand Up @@ -2864,7 +2938,9 @@ ZEND_API zend_result zend_set_memory_limit(size_t memory_limit)
do {
zend_mm_chunk *p = heap->cached_chunks;
heap->cached_chunks = p->next;
zend_mm_chunk_free(heap, p, ZEND_MM_CHUNK_SIZE);
if (!p->preserve) {
zend_mm_chunk_free(heap, p, ZEND_MM_CHUNK_SIZE);
}
heap->cached_chunks_count--;
heap->real_size -= ZEND_MM_CHUNK_SIZE;
} while (memory_limit < heap->real_size);
Expand Down Expand Up @@ -2919,8 +2995,22 @@ ZEND_API void zend_memory_reset_peak_usage(void)
#endif
}

static void alloc_globals_ctor(zend_alloc_globals *alloc_globals);

ZEND_API void shutdown_memory_manager(bool silent, bool full_shutdown)
{
if (!full_shutdown) {
zend_mm_heap *heap = AG(mm_heap);
if (heap->main_chunk->preserve) {
/* The main chunk is preserved, so we can not re-use it in the next
* request: We have to full shutdown and start a new heap.
* This happens when snapshot_state() was called during the request.
*/
zend_mm_shutdown(AG(mm_heap), 1, silent);
alloc_globals_ctor(&alloc_globals);
return;
}
}
zend_mm_shutdown(AG(mm_heap), full_shutdown, silent);
}

Expand Down
11 changes: 10 additions & 1 deletion Zend/zend_alloc.h
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -241,7 +241,8 @@ ZEND_API void zend_memory_reset_peak_usage(void);
efree_size_rel(ht, sizeof(HashTable))

/* Heap functions */
typedef struct _zend_mm_heap zend_mm_heap;
typedef struct _zend_mm_heap zend_mm_heap;
typedef struct _zend_mm_chunk zend_mm_chunk;

ZEND_API zend_mm_heap *zend_mm_startup(void);
ZEND_API void zend_mm_shutdown(zend_mm_heap *heap, bool full_shutdown, bool silent);
Expand Down Expand Up @@ -316,6 +317,14 @@ struct _zend_mm_storage {
ZEND_API zend_mm_storage *zend_mm_get_storage(zend_mm_heap *heap);
ZEND_API zend_mm_heap *zend_mm_startup_ex(const zend_mm_handlers *handlers, void *data, size_t data_size);

ZEND_API zend_mm_chunk *zend_mm_get_chunk_list(zend_mm_heap *heap);
ZEND_API zend_mm_chunk *zend_mm_get_next_chunk(zend_mm_heap *heap, zend_mm_chunk *chunk);
ZEND_API int zend_mm_get_chunks_count(zend_mm_heap *heap);
ZEND_API void zend_mm_adopt_chunk(zend_mm_heap *heap, zend_mm_chunk *chunk);
ZEND_API void *zend_mm_chunk_alloc(zend_mm_heap *heap, size_t size, size_t alignment);
ZEND_API void *zend_mm_get_huge_list(zend_mm_heap *heap);
ZEND_API void zend_mm_preserve_chunk(zend_mm_heap *heap, zend_mm_chunk *chunk);

/*

// The following example shows how to use zend_mm_heap API with custom storage
Expand Down
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