cpython: 37bacf3fa1f5 Objects/obmalloc.c (original) (raw)

Issues #26289 and #26315: Optimize floor/modulo div for single-digit longs Microbenchmarks show 2-2.5x improvement. Built-in 'divmod' function is now also ~10% faster. -m timeit -s "x=22331" "x//2;x//-3;x//4;x//5;x//-6;x//7;x//8;x//-99;x//100;" with patch: 0.321 without patch: 0.633 -m timeit -s "x=22331" "x%2;x%3;x%-4;x%5;x%6;x%-7;x%8;x%99;x%-100;" with patch: 0.224 without patch: 0.66 Big thanks to Serhiy Storchaka, Mark Dickinson and Victor Stinner for thorow code reviews and algorithms improvements. [#26289]

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#include "Python.h" /* Python's malloc wrappers (see pymem.h) / #ifdef PYMALLOC_DEBUG / WITH_PYMALLOC && PYMALLOC_DEBUG / / Forward declaration / static void _PyMem_DebugMalloc(void ctx, size_t size); static void _PyMem_DebugCalloc(void *ctx, size_t nelem, size_t elsize); static void _PyMem_DebugFree(void *ctx, void p); static void _PyMem_DebugRealloc(void *ctx, void *ptr, size_t size); static void _PyObject_DebugDumpAddress(const void *p); static void _PyMem_DebugCheckAddress(char api_id, const void p); #endif #if defined(__has_feature) / Clang / #if __has_feature(address_sanitizer) / is ASAN enabled? / #define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS [](#l18) attribute((no_address_safety_analysis)) [](#l19) attribute ((noinline)) #else #define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS #endif #else #if defined(SANITIZE_ADDRESS) / GCC 4.8.x, is ASAN enabled? */ #define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS [](#l26) attribute((no_address_safety_analysis)) [](#l27) attribute ((noinline)) #else #define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS #endif #endif #ifdef WITH_PYMALLOC #ifdef MS_WINDOWS

include <windows.h>

#elif defined(HAVE_MMAP)

include <sys/mman.h>

ifdef MAP_ANONYMOUS

define ARENAS_USE_MMAP

endif

#endif /* Forward declaration / static void _PyObject_Malloc(void ctx, size_t size); static void _PyObject_Calloc(void *ctx, size_t nelem, size_t elsize); static void _PyObject_Free(void *ctx, void p); static void _PyObject_Realloc(void *ctx, void *ptr, size_t size); #endif static void * _PyMem_RawMalloc(void ctx, size_t size) { / PyMem_RawMalloc(0) means malloc(1). Some systems would return NULL for malloc(0), which would be treated as an error. Some platforms would return a pointer with no memory behind it, which would break pymalloc. To solve these problems, allocate an extra byte. */ if (size == 0) size = 1; return malloc(size); } static void * _PyMem_RawCalloc(void ctx, size_t nelem, size_t elsize) { / PyMem_RawCalloc(0, 0) means calloc(1, 1). Some systems would return NULL for calloc(0, 0), which would be treated as an error. Some platforms would return a pointer with no memory behind it, which would break pymalloc. To solve these problems, allocate an extra byte. */ if (nelem == 0 || elsize == 0) { nelem = 1; elsize = 1; } return calloc(nelem, elsize); } static void * _PyMem_RawRealloc(void *ctx, void *ptr, size_t size) { if (size == 0) size = 1; return realloc(ptr, size); } static void _PyMem_RawFree(void *ctx, void *ptr) { free(ptr); } #ifdef MS_WINDOWS static void * _PyObject_ArenaVirtualAlloc(void *ctx, size_t size) { return VirtualAlloc(NULL, size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE); } static void _PyObject_ArenaVirtualFree(void *ctx, void *ptr, size_t size) { VirtualFree(ptr, 0, MEM_RELEASE); } #elif defined(ARENAS_USE_MMAP) static void * _PyObject_ArenaMmap(void *ctx, size_t size) { void *ptr; ptr = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); if (ptr == MAP_FAILED) return NULL; assert(ptr != NULL); return ptr; } static void _PyObject_ArenaMunmap(void *ctx, void *ptr, size_t size) { munmap(ptr, size); } #else static void * _PyObject_ArenaMalloc(void *ctx, size_t size) { return malloc(size); } static void _PyObject_ArenaFree(void *ctx, void *ptr, size_t size) { free(ptr); } #endif #define PYRAW_FUNCS _PyMem_RawMalloc, _PyMem_RawCalloc, _PyMem_RawRealloc, _PyMem_RawFree #ifdef WITH_PYMALLOC

define PYOBJ_FUNCS _PyObject_Malloc, _PyObject_Calloc, _PyObject_Realloc, _PyObject_Free

#else

define PYOBJ_FUNCS PYRAW_FUNCS

#endif #define PYMEM_FUNCS PYRAW_FUNCS #ifdef PYMALLOC_DEBUG typedef struct { /* We tag each block with an API ID in order to tag API violations */ char api_id; PyMemAllocatorEx alloc; } debug_alloc_api_t; static struct { debug_alloc_api_t raw; debug_alloc_api_t mem; debug_alloc_api_t obj; } _PyMem_Debug = { {'r', {NULL, PYRAW_FUNCS}}, {'m', {NULL, PYMEM_FUNCS}}, {'o', {NULL, PYOBJ_FUNCS}} }; #define PYDBG_FUNCS _PyMem_DebugMalloc, _PyMem_DebugCalloc, _PyMem_DebugRealloc, _PyMem_DebugFree #endif static PyMemAllocatorEx _PyMem_Raw = { #ifdef PYMALLOC_DEBUG &_PyMem_Debug.raw, PYDBG_FUNCS #else NULL, PYRAW_FUNCS #endif }; static PyMemAllocatorEx _PyMem = { #ifdef PYMALLOC_DEBUG &_PyMem_Debug.mem, PYDBG_FUNCS #else NULL, PYMEM_FUNCS #endif }; static PyMemAllocatorEx _PyObject = { #ifdef PYMALLOC_DEBUG &_PyMem_Debug.obj, PYDBG_FUNCS #else NULL, PYOBJ_FUNCS #endif }; #undef PYRAW_FUNCS #undef PYMEM_FUNCS #undef PYOBJ_FUNCS #undef PYDBG_FUNCS static PyObjectArenaAllocator _PyObject_Arena = {NULL, #ifdef MS_WINDOWS _PyObject_ArenaVirtualAlloc, _PyObject_ArenaVirtualFree #elif defined(ARENAS_USE_MMAP) _PyObject_ArenaMmap, _PyObject_ArenaMunmap #else _PyObject_ArenaMalloc, _PyObject_ArenaFree #endif }; void PyMem_SetupDebugHooks(void) { #ifdef PYMALLOC_DEBUG PyMemAllocatorEx alloc; alloc.malloc = _PyMem_DebugMalloc; alloc.calloc = _PyMem_DebugCalloc; alloc.realloc = _PyMem_DebugRealloc; alloc.free = _PyMem_DebugFree; if (_PyMem_Raw.malloc != _PyMem_DebugMalloc) { alloc.ctx = &_PyMem_Debug.raw; PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &_PyMem_Debug.raw.alloc); PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &alloc); } if (_PyMem.malloc != _PyMem_DebugMalloc) { alloc.ctx = &_PyMem_Debug.mem; PyMem_GetAllocator(PYMEM_DOMAIN_MEM, &_PyMem_Debug.mem.alloc); PyMem_SetAllocator(PYMEM_DOMAIN_MEM, &alloc); } if (_PyObject.malloc != _PyMem_DebugMalloc) { alloc.ctx = &_PyMem_Debug.obj; PyMem_GetAllocator(PYMEM_DOMAIN_OBJ, &_PyMem_Debug.obj.alloc); PyMem_SetAllocator(PYMEM_DOMAIN_OBJ, &alloc); } #endif } void PyMem_GetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator) { switch(domain) { case PYMEM_DOMAIN_RAW: *allocator = _PyMem_Raw; break; case PYMEM_DOMAIN_MEM: *allocator = _PyMem; break; case PYMEM_DOMAIN_OBJ: allocator = _PyObject; break; default: / unknown domain: set all attributes to NULL */ allocator->ctx = NULL; allocator->malloc = NULL; allocator->calloc = NULL; allocator->realloc = NULL; allocator->free = NULL; } } void PyMem_SetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator) { switch(domain) { case PYMEM_DOMAIN_RAW: _PyMem_Raw = *allocator; break; case PYMEM_DOMAIN_MEM: _PyMem = *allocator; break; case PYMEM_DOMAIN_OBJ: _PyObject = allocator; break; / ignore unknown domain */ } } void PyObject_GetArenaAllocator(PyObjectArenaAllocator *allocator) { *allocator = _PyObject_Arena; } void PyObject_SetArenaAllocator(PyObjectArenaAllocator *allocator) { _PyObject_Arena = *allocator; } void PyMem_RawMalloc(size_t size) { / * Limit ourselves to PY_SSIZE_T_MAX bytes to prevent security holes. * Most python internals blindly use a signed Py_ssize_t to track * things without checking for overflows or negatives. * As size_t is unsigned, checking for size < 0 is not required. */ if (size > (size_t)PY_SSIZE_T_MAX) return NULL; return _PyMem_Raw.malloc(_PyMem_Raw.ctx, size); } void PyMem_RawCalloc(size_t nelem, size_t elsize) { / see PyMem_RawMalloc() / if (elsize != 0 && nelem > (size_t)PY_SSIZE_T_MAX / elsize) return NULL; return _PyMem_Raw.calloc(_PyMem_Raw.ctx, nelem, elsize); } void PyMem_RawRealloc(void ptr, size_t new_size) { / see PyMem_RawMalloc() */ if (new_size > (size_t)PY_SSIZE_T_MAX) return NULL; return _PyMem_Raw.realloc(_PyMem_Raw.ctx, ptr, new_size); } void PyMem_RawFree(void *ptr) { _PyMem_Raw.free(_PyMem_Raw.ctx, ptr); } void PyMem_Malloc(size_t size) { / see PyMem_RawMalloc() */ if (size > (size_t)PY_SSIZE_T_MAX) return NULL; return _PyMem.malloc(_PyMem.ctx, size); } void PyMem_Calloc(size_t nelem, size_t elsize) { / see PyMem_RawMalloc() */ if (elsize != 0 && nelem > (size_t)PY_SSIZE_T_MAX / elsize) return NULL; return _PyMem.calloc(_PyMem.ctx, nelem, elsize); } void * PyMem_Realloc(void ptr, size_t new_size) { / see PyMem_RawMalloc() */ if (new_size > (size_t)PY_SSIZE_T_MAX) return NULL; return _PyMem.realloc(_PyMem.ctx, ptr, new_size); } void PyMem_Free(void *ptr) { _PyMem.free(_PyMem.ctx, ptr); } char * _PyMem_RawStrdup(const char *str) { size_t size; char *copy; size = strlen(str) + 1; copy = PyMem_RawMalloc(size); if (copy == NULL) return NULL; memcpy(copy, str, size); return copy; } char * _PyMem_Strdup(const char *str) { size_t size; char *copy; size = strlen(str) + 1; copy = PyMem_Malloc(size); if (copy == NULL) return NULL; memcpy(copy, str, size); return copy; } void PyObject_Malloc(size_t size) { / see PyMem_RawMalloc() */ if (size > (size_t)PY_SSIZE_T_MAX) return NULL; return _PyObject.malloc(_PyObject.ctx, size); } void PyObject_Calloc(size_t nelem, size_t elsize) { / see PyMem_RawMalloc() */ if (elsize != 0 && nelem > (size_t)PY_SSIZE_T_MAX / elsize) return NULL; return _PyObject.calloc(_PyObject.ctx, nelem, elsize); } void * PyObject_Realloc(void ptr, size_t new_size) { / see PyMem_RawMalloc() */ if (new_size > (size_t)PY_SSIZE_T_MAX) return NULL; return _PyObject.realloc(_PyObject.ctx, ptr, new_size); } void PyObject_Free(void ptr) { _PyObject.free(_PyObject.ctx, ptr); } #ifdef WITH_PYMALLOC #ifdef WITH_VALGRIND #include <valgrind/valgrind.h> / If we're using GCC, use __builtin_expect() to reduce overhead of the valgrind checks */ #if defined(GNUC) && (GNUC > 2) && defined(OPTIMIZE)

define UNLIKELY(value) __builtin_expect((value), 0)

#else

define UNLIKELY(value) (value)

#endif /* -1 indicates that we haven't checked that we're running on valgrind yet. / static int running_on_valgrind = -1; #endif / An object allocator for Python. Here is an introduction to the layers of the Python memory architecture, showing where the object allocator is actually used (layer +2), It is called for every object allocation and deallocation (PyObject_New/Del), unless the object-specific allocators implement a proprietary allocation scheme (ex.: ints use a simple free list). This is also the place where the cyclic garbage collector operates selectively on container objects. Object-specific allocators _____ ______ ______ _______ [ int ] [ dict ] [ list ] ... [ string ] Python core | +3 | <----- Object-specific memory -----> | <-- Non-object memory --> | _______________________________ | | [ Python's object allocator ] | | +2 | ####### Object memory ####### | <------ Internal buffers ------> | ______________________________________________________________ | [ Python's raw memory allocator (PyMem API) ] | +1 | <----- Python memory (under PyMem manager's control) ------> | | __________________________________________________________________ [ Underlying general-purpose allocator (ex: C library malloc) ] 0 | <------ Virtual memory allocated for the python process -------> | ========================================================================= _______________________________________________________________________ [ OS-specific Virtual Memory Manager (VMM) ] -1 | <--- Kernel dynamic storage allocation & management (page-based) ---> | __________________________________ __________________________________ [ ] [ ] -2 | <-- Physical memory: ROM/RAM --> | | <-- Secondary storage (swap) --> | / /==========================================================================/ / A fast, special-purpose memory allocator for small blocks, to be used on top of a general-purpose malloc -- heavily based on previous art. / / Vladimir Marangozov -- August 2000 / /

/ / #undef WITH_MEMORY_LIMITS / / disable mem limit checks / /==========================================================================/ /

*

/ /==========================================================================/ /

/*

#define ALIGNMENT 8 /* must be 2^N / #define ALIGNMENT_SHIFT 3 / Return the number of bytes in size class I, as a uint. / #define INDEX2SIZE(I) (((uint)(I) + 1) << ALIGNMENT_SHIFT) /

*

#define SMALL_REQUEST_THRESHOLD 512 #define NB_SMALL_SIZE_CLASSES (SMALL_REQUEST_THRESHOLD / ALIGNMENT) /*

#define SYSTEM_PAGE_SIZE (4 * 1024) #define SYSTEM_PAGE_SIZE_MASK (SYSTEM_PAGE_SIZE - 1) /*

#ifdef WITH_MEMORY_LIMITS #ifndef SMALL_MEMORY_LIMIT #define SMALL_MEMORY_LIMIT (64 * 1024 * 1024) /* 64 MB -- more? / #endif #endif /

#define ARENA_SIZE (256 << 10) /* 256KB / #ifdef WITH_MEMORY_LIMITS #define MAX_ARENAS (SMALL_MEMORY_LIMIT / ARENA_SIZE) #endif /

#define POOL_SIZE SYSTEM_PAGE_SIZE /* must be 2^N / #define POOL_SIZE_MASK SYSTEM_PAGE_SIZE_MASK /

/==========================================================================/ /*

/*

#define SIMPLELOCK_DECL(lock) /* simple lock declaration / #define SIMPLELOCK_INIT(lock) / allocate (if needed) and initialize / #define SIMPLELOCK_FINI(lock) / free/destroy an existing lock / #define SIMPLELOCK_LOCK(lock) / acquire released lock / #define SIMPLELOCK_UNLOCK(lock) / release acquired lock / /

#undef uchar #define uchar unsigned char /* assuming == 8 bits / #undef uint #define uint unsigned int / assuming >= 16 bits / #undef ulong #define ulong unsigned long / assuming >= 32 bits / #undef uptr #define uptr Py_uintptr_t / When you say memory, my mind reasons in terms of (pointers to) blocks / typedef uchar block; / Pool for small blocks. */ struct pool_header { union { block _padding; uint count; } ref; / number of allocated blocks / block freeblock; / pool's free list head / struct pool_header nextpool; / next pool of this size class / struct pool_header prevpool; / previous pool "" / uint arenaindex; / index into arenas of base adr / uint szidx; / block size class index / uint nextoffset; / bytes to virgin block / uint maxnextoffset; / largest valid nextoffset / }; typedef struct pool_header poolp; / Record keeping for arenas. / struct arena_object { / The address of the arena, as returned by malloc. Note that 0 * will never be returned by a successful malloc, and is used * here to mark an arena_object that doesn't correspond to an * allocated arena. / uptr address; / Pool-aligned pointer to the next pool to be carved off. / block pool_address; / The number of available pools in the arena: free pools + never- * allocated pools. / uint nfreepools; / The total number of pools in the arena, whether or not available. / uint ntotalpools; / Singly-linked list of available pools. / struct pool_header freepools; / Whenever this arena_object is not associated with an allocated * arena, the nextarena member is used to link all unassociated * arena_objects in the singly-linked unused_arena_objects list. * The prevarena member is unused in this case. * When this arena_object is associated with an allocated arena * with at least one available pool, both members are used in the * doubly-linked usable_arenas list, which is maintained in * increasing order of nfreepools values. * Else this arena_object is associated with an allocated arena * all of whose pools are in use. nextarena and prevarena * are both meaningless in this case. / struct arena_object nextarena; struct arena_object prevarena; }; #define POOL_OVERHEAD _Py_SIZE_ROUND_UP(sizeof(struct pool_header), ALIGNMENT) #define DUMMY_SIZE_IDX 0xffff / size class of newly cached pools / / Round pointer P down to the closest pool-aligned address <= P, as a poolp / #define POOL_ADDR(P) ((poolp)_Py_ALIGN_DOWN((P), POOL_SIZE)) / Return total number of blocks in pool of size index I, as a uint. / #define NUMBLOCKS(I) ((uint)(POOL_SIZE - POOL_OVERHEAD) / INDEX2SIZE(I)) /==========================================================================/ /

#define LOCK() SIMPLELOCK_LOCK(_malloc_lock) #define UNLOCK() SIMPLELOCK_UNLOCK(_malloc_lock) #define LOCK_INIT() SIMPLELOCK_INIT(_malloc_lock) #define LOCK_FINI() SIMPLELOCK_FINI(_malloc_lock) /*

This is involved. For an index i, usedpools[i+i] is the header for a list of all partially used pools holding small blocks with "size class idx" i. So usedpools[0] corresponds to blocks of size 8, usedpools[2] to blocks of size 16, and so on: index 2i <-> blocks of size (i+1)<<ALIGNMENT_SHIFT. Pools are carved off an arena's highwater mark (an arena_object's pool_address member) as needed. Once carved off, a pool is in one of three states forever after: used == partially used, neither empty nor full At least one block in the pool is currently allocated, and at least one block in the pool is not currently allocated (note this implies a pool has room for at least two blocks). This is a pool's initial state, as a pool is created only when malloc needs space. The pool holds blocks of a fixed size, and is in the circular list headed at usedpools[i] (see above). It's linked to the other used pools of the same size class via the pool_header's nextpool and prevpool members. If all but one block is currently allocated, a malloc can cause a transition to the full state. If all but one block is not currently allocated, a free can cause a transition to the empty state. full == all the pool's blocks are currently allocated On transition to full, a pool is unlinked from its usedpools[] list. It's not linked to from anything then anymore, and its nextpool and prevpool members are meaningless until it transitions back to used. A free of a block in a full pool puts the pool back in the used state. Then it's linked in at the front of the appropriate usedpools[] list, so that the next allocation for its size class will reuse the freed block. empty == all the pool's blocks are currently available for allocation On transition to empty, a pool is unlinked from its usedpools[] list, and linked to the front of its arena_object's singly-linked freepools list, via its nextpool member. The prevpool member has no meaning in this case. Empty pools have no inherent size class: the next time a malloc finds an empty list in usedpools[], it takes the first pool off of freepools. If the size class needed happens to be the same as the size class the pool last had, some pool initialization can be skipped. Block Management Blocks within pools are again carved out as needed. pool->freeblock points to the start of a singly-linked list of free blocks within the pool. When a block is freed, it's inserted at the front of its pool's freeblock list. Note that the available blocks in a pool are not linked all together when a pool is initialized. Instead only "the first two" (lowest addresses) blocks are set up, returning the first such block, and setting pool->freeblock to a one-block list holding the second such block. This is consistent with that pymalloc strives at all levels (arena, pool, and block) never to touch a piece of memory until it's actually needed. So long as a pool is in the used state, we're certain there is a block available for allocating, and pool->freeblock is not NULL. If pool->freeblock points to the end of the free list before we've carved the entire pool into blocks, that means we simply haven't yet gotten to one of the higher-address blocks. The offset from the pool_header to the start of "the next" virgin block is stored in the pool_header nextoffset member, and the largest value of nextoffset that makes sense is stored in the maxnextoffset member when a pool is initialized. All the blocks in a pool have been passed out at least once when and only when nextoffset > maxnextoffset. Major obscurity: While the usedpools vector is declared to have poolp entries, it doesn't really. It really contains two pointers per (conceptual) poolp entry, the nextpool and prevpool members of a pool_header. The excruciating initialization code below fools C so that usedpool[i+i] "acts like" a genuine poolp, but only so long as you only reference its nextpool and prevpool members. The "- 2sizeof(block *)" gibberish is compensating for that a pool_header's nextpool and prevpool members immediately follow a pool_header's first two members: union { block *_padding; uint count; } ref; block *freeblock; each of which consume sizeof(block ) bytes. So what usedpools[i+i] really contains is a fudged-up pointer p such that if C believes it's a poolp pointer, then p->nextpool and p->prevpool are both p (meaning that the headed circular list is empty). It's unclear why the usedpools setup is so convoluted. It could be to minimize the amount of cache required to hold this heavily-referenced table (which only needs the two interpool pointer members of a pool_header). OTOH, referencing code has to remember to "double the index" and doing so isn't free, usedpools[0] isn't a strictly legal pointer, and we're crucially relying on that C doesn't insert any padding anywhere in a pool_header at or before the prevpool member. **************************************************************************** / #define PTA(x) ((poolp )((uchar )&(usedpools[2(x)]) - 2sizeof(block ))) #define PT(x) PTA(x), PTA(x) static poolp usedpools[2 * ((NB_SMALL_SIZE_CLASSES + 7) / 8) * 8] = { PT(0), PT(1), PT(2), PT(3), PT(4), PT(5), PT(6), PT(7) #if NB_SMALL_SIZE_CLASSES > 8 , PT(8), PT(9), PT(10), PT(11), PT(12), PT(13), PT(14), PT(15) #if NB_SMALL_SIZE_CLASSES > 16 , PT(16), PT(17), PT(18), PT(19), PT(20), PT(21), PT(22), PT(23) #if NB_SMALL_SIZE_CLASSES > 24 , PT(24), PT(25), PT(26), PT(27), PT(28), PT(29), PT(30), PT(31) #if NB_SMALL_SIZE_CLASSES > 32 , PT(32), PT(33), PT(34), PT(35), PT(36), PT(37), PT(38), PT(39) #if NB_SMALL_SIZE_CLASSES > 40 , PT(40), PT(41), PT(42), PT(43), PT(44), PT(45), PT(46), PT(47) #if NB_SMALL_SIZE_CLASSES > 48 , PT(48), PT(49), PT(50), PT(51), PT(52), PT(53), PT(54), PT(55) #if NB_SMALL_SIZE_CLASSES > 56 , PT(56), PT(57), PT(58), PT(59), PT(60), PT(61), PT(62), PT(63) #if NB_SMALL_SIZE_CLASSES > 64 #error "NB_SMALL_SIZE_CLASSES should be less than 64" #endif / NB_SMALL_SIZE_CLASSES > 64 / #endif / NB_SMALL_SIZE_CLASSES > 56 / #endif / NB_SMALL_SIZE_CLASSES > 48 / #endif / NB_SMALL_SIZE_CLASSES > 40 / #endif / NB_SMALL_SIZE_CLASSES > 32 / #endif / NB_SMALL_SIZE_CLASSES > 24 / #endif / NB_SMALL_SIZE_CLASSES > 16 / #endif / NB_SMALL_SIZE_CLASSES > 8 / }; /========================================================================== Arena management. arenas is a vector of arena_objects. It contains maxarenas entries, some of which may not be currently used (== they're arena_objects that aren't currently associated with an allocated arena). Note that arenas proper are separately malloc'ed. Prior to Python 2.5, arenas were never free()'ed. Starting with Python 2.5, we do try to free() arenas, and use some mild heuristic strategies to increase the likelihood that arenas eventually can be freed. unused_arena_objects This is a singly-linked list of the arena_objects that are currently not being used (no arena is associated with them). Objects are taken off the head of the list in new_arena(), and are pushed on the head of the list in PyObject_Free() when the arena is empty. Key invariant: an arena_object is on this list if and only if its .address member is 0. usable_arenas This is a doubly-linked list of the arena_objects associated with arenas that have pools available. These pools are either waiting to be reused, or have not been used before. The list is sorted to have the most- allocated arenas first (ascending order based on the nfreepools member). This means that the next allocation will come from a heavily used arena, which gives the nearly empty arenas a chance to be returned to the system. In my unscientific tests this dramatically improved the number of arenas that could be freed. Note that an arena_object associated with an arena all of whose pools are currently in use isn't on either list. / / Array of objects used to track chunks of memory (arenas). / static struct arena_object arenas = NULL; / Number of slots currently allocated in the arenas vector. / static uint maxarenas = 0; / The head of the singly-linked, NULL-terminated list of available

/* The head of the doubly-linked, NULL-terminated at each end, list of

/* How many arena_objects do we initially allocate?

#define INITIAL_ARENA_OBJECTS 16 /* Number of arenas allocated that haven't been free()'d. / static size_t narenas_currently_allocated = 0; / Total number of times malloc() called to allocate an arena. / static size_t ntimes_arena_allocated = 0; / High water mark (max value ever seen) for narenas_currently_allocated. / static size_t narenas_highwater = 0; static Py_ssize_t _Py_AllocatedBlocks = 0; Py_ssize_t _Py_GetAllocatedBlocks(void) { return _Py_AllocatedBlocks; } / Allocate a new arena. If we run out of memory, return NULL. Else

#ifdef PYMALLOC_DEBUG if (Py_GETENV("PYTHONMALLOCSTATS")) _PyObject_DebugMallocStats(stderr); #endif if (unused_arena_objects == NULL) { uint i; uint numarenas; size_t nbytes; /* Double the number of arena objects on each allocation. * Note that it's possible for numarenas to overflow. */ numarenas = maxarenas ? maxarenas << 1 : INITIAL_ARENA_OBJECTS; if (numarenas <= maxarenas) return NULL; /* overflow */ #if SIZEOF_SIZE_T <= SIZEOF_INT if (numarenas > PY_SIZE_MAX / sizeof(arenas)) return NULL; / overflow / #endif nbytes = numarenas * sizeof(arenas); arenaobj = (struct arena_object )PyMem_RawRealloc(arenas, nbytes); if (arenaobj == NULL) return NULL; arenas = arenaobj; / We might need to fix pointers that were copied. However, * new_arena only gets called when all the pages in the * previous arenas are full. Thus, there are no pointers * into the old array. Thus, we don't have to worry about * invalid pointers. Just to be sure, some asserts: / assert(usable_arenas == NULL); assert(unused_arena_objects == NULL); / Put the new arenas on the unused_arena_objects list. / for (i = maxarenas; i < numarenas; ++i) { arenas[i].address = 0; /* mark as unassociated */ arenas[i].nextarena = i < numarenas - 1 ? &arenas[i+1] : NULL; } /* Update globals. */ unused_arena_objects = &arenas[maxarenas]; maxarenas = numarenas; } /* Take the next available arena object off the head of the list. */ assert(unused_arena_objects != NULL); arenaobj = unused_arena_objects; unused_arena_objects = arenaobj->nextarena; assert(arenaobj->address == 0); address = _PyObject_Arena.alloc(_PyObject_Arena.ctx, ARENA_SIZE); if (address == NULL) { / The allocation failed: return NULL after putting the * arenaobj back. / arenaobj->nextarena = unused_arena_objects; unused_arena_objects = arenaobj; return NULL; } arenaobj->address = (uptr)address; ++narenas_currently_allocated; ++ntimes_arena_allocated; if (narenas_currently_allocated > narenas_highwater) narenas_highwater = narenas_currently_allocated; arenaobj->freepools = NULL; / pool_address <- first pool-aligned address in the arena nfreepools <- number of whole pools that fit after alignment */ arenaobj->pool_address = (block)arenaobj->address; arenaobj->nfreepools = ARENA_SIZE / POOL_SIZE; assert(POOL_SIZE * arenaobj->nfreepools == ARENA_SIZE); excess = (uint)(arenaobj->address & POOL_SIZE_MASK); if (excess != 0) { --arenaobj->nfreepools; arenaobj->pool_address += POOL_SIZE - excess; } arenaobj->ntotalpools = arenaobj->nfreepools; return arenaobj; } / Py_ADDRESS_IN_RANGE(P, POOL) Return true if and only if P is an address that was allocated by pymalloc. POOL must be the pool address associated with P, i.e., POOL = POOL_ADDR(P) (the caller is asked to compute this because the macro expands POOL more than once, and for efficiency it's best for the caller to assign POOL_ADDR(P) to a variable and pass the latter to the macro; because Py_ADDRESS_IN_RANGE is called on every alloc/realloc/free, micro-efficiency is important here). Tricky: Let B be the arena base address associated with the pool, B = arenas[(POOL)->arenaindex].address. Then P belongs to the arena if and only if B <= P < B + ARENA_SIZE Subtracting B throughout, this is true iff 0 <= P-B < ARENA_SIZE By using unsigned arithmetic, the "0 <=" half of the test can be skipped. Obscure: A PyMem "free memory" function can call the pymalloc free or realloc before the first arena has been allocated. arenas is still NULL in that case. We're relying on that maxarenas is also 0 in that case, so that (POOL)->arenaindex < maxarenas must be false, saving us from trying to index into a NULL arenas. Details: given P and POOL, the arena_object corresponding to P is AO = arenas[(POOL)->arenaindex]. Suppose obmalloc controls P. Then (barring wild stores, etc), POOL is the correct address of P's pool, AO.address is the correct base address of the pool's arena, and P must be within ARENA_SIZE of AO.address. In addition, AO.address is not 0 (no arena can start at address 0 (NULL)). Therefore Py_ADDRESS_IN_RANGE correctly reports that obmalloc controls P. Now suppose obmalloc does not control P (e.g., P was obtained via a direct call to the system malloc() or realloc()). (POOL)->arenaindex may be anything in this case -- it may even be uninitialized trash. If the trash arenaindex is >= maxarenas, the macro correctly concludes at once that obmalloc doesn't control P. Else arenaindex is < maxarena, and AO is read up. If AO corresponds to an allocated arena, obmalloc controls all the memory in slice AO.address : AO.address+ARENA_SIZE. By case assumption, P is not controlled by obmalloc, so P doesn't lie in that slice, so the macro correctly reports that P is not controlled by obmalloc. Finally, if P is not controlled by obmalloc and AO corresponds to an unused arena_object (one not currently associated with an allocated arena), AO.address is 0, and the second test in the macro reduces to: P < ARENA_SIZE If P >= ARENA_SIZE (extremely likely), the macro again correctly concludes that P is not controlled by obmalloc. However, if P < ARENA_SIZE, this part of the test still passes, and the third clause (AO.address != 0) is necessary to get the correct result: AO.address is 0 in this case, so the macro correctly reports that P is not controlled by obmalloc (despite that P lies in slice AO.address : AO.address + ARENA_SIZE). Note: The third (AO.address != 0) clause was added in Python 2.5. Before 2.5, arenas were never free()'ed, and an arenaindex < maxarena always corresponded to a currently-allocated arena, so the "P is not controlled by obmalloc, AO corresponds to an unused arena_object, and P < ARENA_SIZE" case was impossible. Note that the logic is excruciating, and reading up possibly uninitialized memory when P is not controlled by obmalloc (to get at (POOL)->arenaindex) creates problems for some memory debuggers. The overwhelming advantage is that this test determines whether an arbitrary address is controlled by obmalloc in a small constant time, independent of the number of arenas obmalloc controls. Since this test is needed at every entry point, it's extremely desirable that it be this fast. Since Py_ADDRESS_IN_RANGE may be reading from memory which was not allocated by Python, it is important that (POOL)->arenaindex is read only once, as another thread may be concurrently modifying the value without holding the GIL. To accomplish this, the arenaindex_temp variable is used to store (POOL)->arenaindex for the duration of the Py_ADDRESS_IN_RANGE macro's execution. The caller of the macro is responsible for declaring this variable. / #define Py_ADDRESS_IN_RANGE(P, POOL) [](#l1117) ((arenaindex_temp = (POOL)->arenaindex) < maxarenas && [](#l1118) (uptr)(P) - arenas[arenaindex_temp].address < (uptr)ARENA_SIZE && [](#l1119) arenas[arenaindex_temp].address != 0) / This is only useful when running memory debuggers such as

#define Py_USING_MEMORY_DEBUGGER / #ifdef Py_USING_MEMORY_DEBUGGER / Py_ADDRESS_IN_RANGE may access uninitialized memory by design

#undef Py_ADDRESS_IN_RANGE #if defined(GNUC) && ((GNUC == 3) && (GNUC_MINOR >= 1) || [](#l1142) (GNUC >= 4)) #define Py_NO_INLINE attribute((noinline)) #else #define Py_NO_INLINE #endif /* Don't make static, to try to ensure this isn't inlined. / int Py_ADDRESS_IN_RANGE(void P, poolp pool) Py_NO_INLINE; #undef Py_NO_INLINE #endif /==========================================================================/ /* malloc. Note that nbytes==0 tries to return a non-NULL pointer, distinct

/*

static void * _PyObject_Alloc(int use_calloc, void *ctx, size_t nelem, size_t elsize) { size_t nbytes; block bp; poolp pool; poolp next; uint size; _Py_AllocatedBlocks++; assert(nelem <= PY_SSIZE_T_MAX / elsize); nbytes = nelem * elsize; #ifdef WITH_VALGRIND if (UNLIKELY(running_on_valgrind == -1)) running_on_valgrind = RUNNING_ON_VALGRIND; if (UNLIKELY(running_on_valgrind)) goto redirect; #endif if (nelem == 0 || elsize == 0) goto redirect; if ((nbytes - 1) < SMALL_REQUEST_THRESHOLD) { LOCK(); /* * Most frequent paths first */ size = (uint)(nbytes - 1) >> ALIGNMENT_SHIFT; pool = usedpools[size + size]; if (pool != pool->nextpool) { / * There is a used pool for this size class. * Pick up the head block of its free list. */ ++pool->ref.count; bp = pool->freeblock; assert(bp != NULL); if ((pool->freeblock = *(block **)bp) != NULL) { UNLOCK(); if (use_calloc) memset(bp, 0, nbytes); return (void )bp; } / * Reached the end of the free list, try to extend it. / if (pool->nextoffset <= pool->maxnextoffset) { / There is room for another block. / pool->freeblock = (block)pool + pool->nextoffset; pool->nextoffset += INDEX2SIZE(size); *(block **)(pool->freeblock) = NULL; UNLOCK(); if (use_calloc) memset(bp, 0, nbytes); return (void )bp; } / Pool is full, unlink from used pools. */ next = pool->nextpool; pool = pool->prevpool; next->prevpool = pool; pool->nextpool = next; UNLOCK(); if (use_calloc) memset(bp, 0, nbytes); return (void )bp; } / There isn't a pool of the right size class immediately * available: use a free pool. / if (usable_arenas == NULL) { / No arena has a free pool: allocate a new arena. / #ifdef WITH_MEMORY_LIMITS if (narenas_currently_allocated >= MAX_ARENAS) { UNLOCK(); goto redirect; } #endif usable_arenas = new_arena(); if (usable_arenas == NULL) { UNLOCK(); goto redirect; } usable_arenas->nextarena = usable_arenas->prevarena = NULL; } assert(usable_arenas->address != 0); / Try to get a cached free pool. / pool = usable_arenas->freepools; if (pool != NULL) { / Unlink from cached pools. / usable_arenas->freepools = pool->nextpool; / This arena already had the smallest nfreepools * value, so decreasing nfreepools doesn't change * that, and we don't need to rearrange the * usable_arenas list. However, if the arena has * become wholly allocated, we need to remove its * arena_object from usable_arenas. / --usable_arenas->nfreepools; if (usable_arenas->nfreepools == 0) { / Wholly allocated: remove. / assert(usable_arenas->freepools == NULL); assert(usable_arenas->nextarena == NULL || usable_arenas->nextarena->prevarena == usable_arenas); usable_arenas = usable_arenas->nextarena; if (usable_arenas != NULL) { usable_arenas->prevarena = NULL; assert(usable_arenas->address != 0); } } else { / nfreepools > 0: it must be that freepools * isn't NULL, or that we haven't yet carved * off all the arena's pools for the first * time. / assert(usable_arenas->freepools != NULL || usable_arenas->pool_address <= (block*)usable_arenas->address + ARENA_SIZE - POOL_SIZE); } init_pool: / Frontlink to used pools. / next = usedpools[size + size]; / == prev / pool->nextpool = next; pool->prevpool = next; next->nextpool = pool; next->prevpool = pool; pool->ref.count = 1; if (pool->szidx == size) { / Luckily, this pool last contained blocks * of the same size class, so its header * and free list are already initialized. */ bp = pool->freeblock; assert(bp != NULL); pool->freeblock = *(block **)bp; UNLOCK(); if (use_calloc) memset(bp, 0, nbytes); return (void )bp; } / * Initialize the pool header, set up the free list to * contain just the second block, and return the first * block. */ pool->szidx = size; size = INDEX2SIZE(size); bp = (block *)pool + POOL_OVERHEAD; pool->nextoffset = POOL_OVERHEAD + (size << 1); pool->maxnextoffset = POOL_SIZE - size; pool->freeblock = bp + size; *(block **)(pool->freeblock) = NULL; UNLOCK(); if (use_calloc) memset(bp, 0, nbytes); return (void )bp; } / Carve off a new pool. / assert(usable_arenas->nfreepools > 0); assert(usable_arenas->freepools == NULL); pool = (poolp)usable_arenas->pool_address; assert((block)pool <= (block*)usable_arenas->address + ARENA_SIZE - POOL_SIZE); pool->arenaindex = (uint)(usable_arenas - arenas); assert(&arenas[pool->arenaindex] == usable_arenas); pool->szidx = DUMMY_SIZE_IDX; usable_arenas->pool_address += POOL_SIZE; --usable_arenas->nfreepools; if (usable_arenas->nfreepools == 0) { assert(usable_arenas->nextarena == NULL || usable_arenas->nextarena->prevarena == usable_arenas); /* Unlink the arena: it is completely allocated. / usable_arenas = usable_arenas->nextarena; if (usable_arenas != NULL) { usable_arenas->prevarena = NULL; assert(usable_arenas->address != 0); } } goto init_pool; } / The small block allocator ends here. / redirect: / Redirect the original request to the underlying (libc) allocator. * We jump here on bigger requests, on error in the code above (as a * last chance to serve the request) or when the max memory limit * has been reached. */ { void *result; if (use_calloc) result = PyMem_RawCalloc(nelem, elsize); else result = PyMem_RawMalloc(nbytes); if (!result) _Py_AllocatedBlocks--; return result; } } static void * _PyObject_Malloc(void *ctx, size_t nbytes) { return _PyObject_Alloc(0, ctx, 1, nbytes); } static void * _PyObject_Calloc(void ctx, size_t nelem, size_t elsize) { return _PyObject_Alloc(1, ctx, nelem, elsize); } / free */ ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS static void _PyObject_Free(void *ctx, void *p) { poolp pool; block lastfree; poolp next, prev; uint size; #ifndef Py_USING_MEMORY_DEBUGGER uint arenaindex_temp; #endif if (p == NULL) / free(NULL) has no effect / return; _Py_AllocatedBlocks--; #ifdef WITH_VALGRIND if (UNLIKELY(running_on_valgrind > 0)) goto redirect; #endif pool = POOL_ADDR(p); if (Py_ADDRESS_IN_RANGE(p, pool)) { / We allocated this address. / LOCK(); / Link p to the start of the pool's freeblock list. Since * the pool had at least the p block outstanding, the pool * wasn't empty (so it's already in a usedpools[] list, or * was full and is in no list -- it's not in the freeblocks * list in any case). / assert(pool->ref.count > 0); / else it was empty */ *(block **)p = lastfree = pool->freeblock; pool->freeblock = (block )p; if (lastfree) { struct arena_object ao; uint nf; /* ao->nfreepools / / freeblock wasn't NULL, so the pool wasn't full, * and the pool is in a usedpools[] list. / if (--pool->ref.count != 0) { / pool isn't empty: leave it in usedpools / UNLOCK(); return; } / Pool is now empty: unlink from usedpools, and * link to the front of freepools. This ensures that * previously freed pools will be allocated later * (being not referenced, they are perhaps paged out). / next = pool->nextpool; prev = pool->prevpool; next->prevpool = prev; prev->nextpool = next; / Link the pool to freepools. This is a singly-linked * list, and pool->prevpool isn't used there. / ao = &arenas[pool->arenaindex]; pool->nextpool = ao->freepools; ao->freepools = pool; nf = ++ao->nfreepools; / All the rest is arena management. We just freed * a pool, and there are 4 cases for arena mgmt: * 1. If all the pools are free, return the arena to * the system free(). * 2. If this is the only free pool in the arena, * add the arena back to the usable_arenas list. * 3. If the "next" arena has a smaller count of free * pools, we have to "slide this arena right" to * restore that usable_arenas is sorted in order of * nfreepools. * 4. Else there's nothing more to do. / if (nf == ao->ntotalpools) { / Case 1. First unlink ao from usable_arenas. / assert(ao->prevarena == NULL || ao->prevarena->address != 0); assert(ao ->nextarena == NULL || ao->nextarena->address != 0); / Fix the pointer in the prevarena, or the * usable_arenas pointer. / if (ao->prevarena == NULL) { usable_arenas = ao->nextarena; assert(usable_arenas == NULL || usable_arenas->address != 0); } else { assert(ao->prevarena->nextarena == ao); ao->prevarena->nextarena = ao->nextarena; } / Fix the pointer in the nextarena. / if (ao->nextarena != NULL) { assert(ao->nextarena->prevarena == ao); ao->nextarena->prevarena = ao->prevarena; } / Record that this arena_object slot is * available to be reused. / ao->nextarena = unused_arena_objects; unused_arena_objects = ao; / Free the entire arena. */ _PyObject_Arena.free(_PyObject_Arena.ctx, (void )ao->address, ARENA_SIZE); ao->address = 0; / mark unassociated / --narenas_currently_allocated; UNLOCK(); return; } if (nf == 1) { / Case 2. Put ao at the head of * usable_arenas. Note that because * ao->nfreepools was 0 before, ao isn't * currently on the usable_arenas list. / ao->nextarena = usable_arenas; ao->prevarena = NULL; if (usable_arenas) usable_arenas->prevarena = ao; usable_arenas = ao; assert(usable_arenas->address != 0); UNLOCK(); return; } / If this arena is now out of order, we need to keep * the list sorted. The list is kept sorted so that * the "most full" arenas are used first, which allows * the nearly empty arenas to be completely freed. In * a few un-scientific tests, it seems like this * approach allowed a lot more memory to be freed. / if (ao->nextarena == NULL || nf <= ao->nextarena->nfreepools) { / Case 4. Nothing to do. / UNLOCK(); return; } / Case 3: We have to move the arena towards the end * of the list, because it has more free pools than * the arena to its right. * First unlink ao from usable_arenas. / if (ao->prevarena != NULL) { / ao isn't at the head of the list / assert(ao->prevarena->nextarena == ao); ao->prevarena->nextarena = ao->nextarena; } else { / ao is at the head of the list / assert(usable_arenas == ao); usable_arenas = ao->nextarena; } ao->nextarena->prevarena = ao->prevarena; / Locate the new insertion point by iterating over * the list, using our nextarena pointer. / while (ao->nextarena != NULL && nf > ao->nextarena->nfreepools) { ao->prevarena = ao->nextarena; ao->nextarena = ao->nextarena->nextarena; } / Insert ao at this point. / assert(ao->nextarena == NULL || ao->prevarena == ao->nextarena->prevarena); assert(ao->prevarena->nextarena == ao->nextarena); ao->prevarena->nextarena = ao; if (ao->nextarena != NULL) ao->nextarena->prevarena = ao; / Verify that the swaps worked. / assert(ao->nextarena == NULL || nf <= ao->nextarena->nfreepools); assert(ao->prevarena == NULL || nf > ao->prevarena->nfreepools); assert(ao->nextarena == NULL || ao->nextarena->prevarena == ao); assert((usable_arenas == ao && ao->prevarena == NULL) || ao->prevarena->nextarena == ao); UNLOCK(); return; } / Pool was full, so doesn't currently live in any list: * link it to the front of the appropriate usedpools[] list. * This mimics LRU pool usage for new allocations and * targets optimal filling when several pools contain * blocks of the same size class. / --pool->ref.count; assert(pool->ref.count > 0); / else the pool is empty / size = pool->szidx; next = usedpools[size + size]; prev = next->prevpool; / insert pool before next: prev <-> pool <-> next / pool->nextpool = next; pool->prevpool = prev; next->prevpool = pool; prev->nextpool = pool; UNLOCK(); return; } #ifdef WITH_VALGRIND redirect: #endif / We didn't allocate this address. / PyMem_RawFree(p); } / realloc. If p is NULL, this acts like malloc(nbytes). Else if nbytes==0,

ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS static void * _PyObject_Realloc(void ctx, void p, size_t nbytes) { void bp; poolp pool; size_t size; #ifndef Py_USING_MEMORY_DEBUGGER uint arenaindex_temp; #endif if (p == NULL) return _PyObject_Alloc(0, ctx, 1, nbytes); #ifdef WITH_VALGRIND / Treat running_on_valgrind == -1 the same as 0 / if (UNLIKELY(running_on_valgrind > 0)) goto redirect; #endif pool = POOL_ADDR(p); if (Py_ADDRESS_IN_RANGE(p, pool)) { / We're in charge of this block / size = INDEX2SIZE(pool->szidx); if (nbytes <= size) { /* The block is staying the same or shrinking. If * it's shrinking, there's a tradeoff: it costs * cycles to copy the block to a smaller size class, * but it wastes memory not to copy it. The * compromise here is to copy on shrink only if at * least 25% of size can be shaved off. */ if (4 * nbytes > 3 * size) { / It's the same, * or shrinking and new/old > 3/4. / return p; } size = nbytes; } bp = _PyObject_Alloc(0, ctx, 1, nbytes); if (bp != NULL) { memcpy(bp, p, size); _PyObject_Free(ctx, p); } return bp; } #ifdef WITH_VALGRIND redirect: #endif / We're not managing this block. If nbytes <= * SMALL_REQUEST_THRESHOLD, it's tempting to try to take over this * block. However, if we do, we need to copy the valid data from * the C-managed block to one of our blocks, and there's no portable * way to know how much of the memory space starting at p is valid. * As bug 1185883 pointed out the hard way, it's possible that the * C-managed block is "at the end" of allocated VM space, so that * a memory fault can occur if we try to copy nbytes bytes starting * at p. Instead we punt: let C continue to manage this block. / if (nbytes) return PyMem_RawRealloc(p, nbytes); / C doesn't define the result of realloc(p, 0) (it may or may not * return NULL then), but Python's docs promise that nbytes==0 never * returns NULL. We don't pass 0 to realloc(), to avoid that endcase * to begin with. Even then, we can't be sure that realloc() won't * return NULL. / bp = PyMem_RawRealloc(p, 1); return bp ? bp : p; } #else / ! WITH_PYMALLOC / /==========================================================================/ / pymalloc not enabled: Redirect the entry points to malloc. These will

Py_ssize_t _Py_GetAllocatedBlocks(void) { return 0; } #endif /* WITH_PYMALLOC / #ifdef PYMALLOC_DEBUG /==========================================================================/ / A x-platform debugging allocator. This doesn't manage memory directly,

/* Special bytes broadcast into debug memory blocks at appropriate times.

#undef CLEANBYTE #undef DEADBYTE #undef FORBIDDENBYTE #define CLEANBYTE 0xCB /* clean (newly allocated) memory / #define DEADBYTE 0xDB / dead (newly freed) memory / #define FORBIDDENBYTE 0xFB / untouchable bytes at each end of a block / static size_t serialno = 0; / incremented on each debug {m,re}alloc / / serialno is always incremented via calling this routine. The point is

#define SST SIZEOF_SIZE_T /* Read sizeof(size_t) bytes at p as a big-endian size_t. */ static size_t read_size_t(const void *p) { const uchar *q = (const uchar *)p; size_t result = *q++; int i; for (i = SST; --i > 0; ++q) result = (result << 8) | q; return result; } / Write n as a big-endian size_t, MSB at address p, LSB at

#ifdef Py_DEBUG /* Is target in the list? The list is traversed via the nextpool pointers.

#else #define pool_is_in_list(X, Y) 1 #endif /* Py_DEBUG / / Let S = sizeof(size_t). The debug malloc asks for 4S extra bytes and fills them with useful stuff, here calling the underlying malloc's result p: p[0: S] Number of bytes originally asked for. This is a size_t, big-endian (easier to read in a memory dump). p[S] API ID. See PEP 445. This is a character, but seems undocumented. p[S+1: 2S] Copies of FORBIDDENBYTE. Used to catch under- writes and reads. p[2S: 2S+n] The requested memory, filled with copies of CLEANBYTE. Used to catch reference to uninitialized memory. &p[2S] is returned. Note that this is 8-byte aligned if pymalloc handled the request itself. p[2S+n: 2S+n+S] Copies of FORBIDDENBYTE. Used to catch over- writes and reads. p[2S+n+S: 2S+n+2S] A serial number, incremented by 1 on each call to _PyMem_DebugMalloc and _PyMem_DebugRealloc. This is a big-endian size_t. If "bad memory" is detected later, the serial number gives an excellent way to set a breakpoint on the next run, to capture the instant at which this block was passed out. */ static void * _PyMem_DebugAlloc(int use_calloc, void ctx, size_t nbytes) { debug_alloc_api_t api = (debug_alloc_api_t )ctx; uchar p; / base address of malloc'ed block / uchar tail; / p + 2SST + nbytes == pointer to tail pad bytes / size_t total; / nbytes + 4SST / bumpserialno(); total = nbytes + 4SST; if (nbytes > PY_SSIZE_T_MAX - 4SST) / overflow: can't represent total as a Py_ssize_t / return NULL; if (use_calloc) p = (uchar )api->alloc.calloc(api->alloc.ctx, 1, total); else p = (uchar )api->alloc.malloc(api->alloc.ctx, total); if (p == NULL) return NULL; / at p, write size (SST bytes), id (1 byte), pad (SST-1 bytes) / write_size_t(p, nbytes); p[SST] = (uchar)api->api_id; memset(p + SST + 1, FORBIDDENBYTE, SST-1); if (nbytes > 0 && !use_calloc) memset(p + 2SST, CLEANBYTE, nbytes); / at tail, write pad (SST bytes) and serialno (SST bytes) / tail = p + 2SST + nbytes; memset(tail, FORBIDDENBYTE, SST); write_size_t(tail + SST, serialno); return p + 2SST; } static void * _PyMem_DebugMalloc(void *ctx, size_t nbytes) { return _PyMem_DebugAlloc(0, ctx, nbytes); } static void * _PyMem_DebugCalloc(void ctx, size_t nelem, size_t elsize) { size_t nbytes; assert(elsize == 0 || nelem <= PY_SSIZE_T_MAX / elsize); nbytes = nelem * elsize; return _PyMem_DebugAlloc(1, ctx, nbytes); } /* The debug free first checks the 2*SST bytes on each end for sanity (in particular, that the FORBIDDENBYTEs with the api ID are still intact). Then fills the original bytes with DEADBYTE. Then calls the underlying free. */ static void _PyMem_DebugFree(void *ctx, void *p) { debug_alloc_api_t *api = (debug_alloc_api_t *)ctx; uchar *q = (uchar *)p - 2*SST; /* address returned from malloc */ size_t nbytes; if (p == NULL) return; _PyMem_DebugCheckAddress(api->api_id, p); nbytes = read_size_t(q); nbytes += 4SST; if (nbytes > 0) memset(q, DEADBYTE, nbytes); api->alloc.free(api->alloc.ctx, q); } static void * _PyMem_DebugRealloc(void *ctx, void *p, size_t nbytes) { debug_alloc_api_t *api = (debug_alloc_api_t )ctx; uchar q = (uchar )p, oldq; uchar tail; size_t total; / nbytes + 4SST / size_t original_nbytes; int i; if (p == NULL) return _PyMem_DebugAlloc(0, ctx, nbytes); _PyMem_DebugCheckAddress(api->api_id, p); bumpserialno(); original_nbytes = read_size_t(q - 2SST); total = nbytes + 4SST; if (nbytes > PY_SSIZE_T_MAX - 4SST) / overflow: can't represent total as a Py_ssize_t / return NULL; / Resize and add decorations. We may get a new pointer here, in which * case we didn't get the chance to mark the old memory with DEADBYTE, * but we live with that. / oldq = q; q = (uchar )api->alloc.realloc(api->alloc.ctx, q - 2SST, total); if (q == NULL) return NULL; if (q == oldq && nbytes < original_nbytes) { /* shrinking: mark old extra memory dead */ memset(q + nbytes, DEADBYTE, original_nbytes - nbytes); } write_size_t(q, nbytes); assert(q[SST] == (uchar)api->api_id); for (i = 1; i < SST; ++i) assert(q[SST + i] == FORBIDDENBYTE); q += 2*SST; tail = q + nbytes; memset(tail, FORBIDDENBYTE, SST); write_size_t(tail + SST, serialno); if (nbytes > original_nbytes) { / growing: mark new extra memory clean / memset(q + original_nbytes, CLEANBYTE, nbytes - original_nbytes); } return q; } / Check the forbidden bytes on both ends of the memory allocated for p.

error: _PyObject_DebugDumpAddress(p); Py_FatalError(msg); } /* Display info to stderr about the memory block at p. */ static void _PyObject_DebugDumpAddress(const void *p) { const uchar *q = (const uchar )p; const uchar tail; size_t nbytes, serial; int i; int ok; char id; fprintf(stderr, "Debug memory block at address p=%p:", p); if (p == NULL) { fprintf(stderr, "\n"); return; } id = (char)q[-SST]; fprintf(stderr, " API '%c'\n", id); nbytes = read_size_t(q - 2SST); fprintf(stderr, " %" PY_FORMAT_SIZE_T "u bytes originally " "requested\n", nbytes); / In case this is nuts, check the leading pad bytes first. */ fprintf(stderr, " The %d pad bytes at p-%d are ", SST-1, SST-1); ok = 1; for (i = 1; i <= SST-1; ++i) { if (*(q-i) != FORBIDDENBYTE) { ok = 0; break; } } if (ok) fputs("FORBIDDENBYTE, as expected.\n", stderr); else { fprintf(stderr, "not all FORBIDDENBYTE (0x%02x):\n", FORBIDDENBYTE); for (i = SST-1; i >= 1; --i) { const uchar byte = (q-i); fprintf(stderr, " at p-%d: 0x%02x", i, byte); if (byte != FORBIDDENBYTE) fputs(" *** OUCH", stderr); fputc('\n', stderr); } fputs(" Because memory is corrupted at the start, the " "count of bytes requested\n" " may be bogus, and checking the trailing pad " "bytes may segfault.\n", stderr); } tail = q + nbytes; fprintf(stderr, " The %d pad bytes at tail=%p are ", SST, tail); ok = 1; for (i = 0; i < SST; ++i) { if (tail[i] != FORBIDDENBYTE) { ok = 0; break; } } if (ok) fputs("FORBIDDENBYTE, as expected.\n", stderr); else { fprintf(stderr, "not all FORBIDDENBYTE (0x%02x):\n", FORBIDDENBYTE); for (i = 0; i < SST; ++i) { const uchar byte = tail[i]; fprintf(stderr, " at tail+%d: 0x%02x", i, byte); if (byte != FORBIDDENBYTE) fputs(" *** OUCH", stderr); fputc('\n', stderr); } } serial = read_size_t(tail + SST); fprintf(stderr, " The block was made by call #%" PY_FORMAT_SIZE_T "u to debug malloc/realloc.\n", serial); if (nbytes > 0) { i = 0; fputs(" Data at p:", stderr); / print up to 8 bytes at the start */ while (q < tail && i < 8) { fprintf(stderr, " %02x", *q); ++i; ++q; } /* and up to 8 at the end */ if (q < tail) { if (tail - q > 8) { fputs(" ...", stderr); q = tail - 8; } while (q < tail) { fprintf(stderr, " %02x", *q); ++q; } } fputc('\n', stderr); } } #endif /* PYMALLOC_DEBUG */ static size_t printone(FILE *out, const char* msg, size_t value) { int i, k; char buf[100]; size_t origvalue = value; fputs(msg, out); for (i = (int)strlen(msg); i < 35; ++i) fputc(' ', out); fputc('=', out); /* Write the value with commas. */ i = 22; buf[i--] = '\0'; buf[i--] = '\n'; k = 3; do { size_t nextvalue = value / 10; unsigned int digit = (unsigned int)(value - nextvalue * 10); value = nextvalue; buf[i--] = (char)(digit + '0'); --k; if (k == 0 && value && i >= 0) { k = 3; buf[i--] = ','; } } while (value && i >= 0); while (i >= 0) buf[i--] = ' '; fputs(buf, out); return origvalue; } void _PyDebugAllocatorStats(FILE *out, const char block_name, int num_blocks, size_t sizeof_block) { char buf1[128]; char buf2[128]; PyOS_snprintf(buf1, sizeof(buf1), "%d %ss * %" PY_FORMAT_SIZE_T "d bytes each", num_blocks, block_name, sizeof_block); PyOS_snprintf(buf2, sizeof(buf2), "%48s ", buf1); (void)printone(out, buf2, num_blocks * sizeof_block); } #ifdef WITH_PYMALLOC / Print summary info to "out" about the state of pymalloc's structures.

for (i = 0; i < numclasses; ++i) numpools[i] = numblocks[i] = numfreeblocks[i] = 0; /* Because full pools aren't linked to from anything, it's easiest * to march over all the arenas. If we're lucky, most of the memory * will be living in full pools -- would be a shame to miss them. / for (i = 0; i < maxarenas; ++i) { uint j; uptr base = arenas[i].address; /* Skip arenas which are not allocated. */ if (arenas[i].address == (uptr)NULL) continue; narenas += 1; numfreepools += arenas[i].nfreepools; /* round up to pool alignment */ if (base & (uptr)POOL_SIZE_MASK) { arena_alignment += POOL_SIZE; base &= ~(uptr)POOL_SIZE_MASK; base += POOL_SIZE; } /* visit every pool in the arena */ assert(base <= (uptr) arenas[i].pool_address); for (j = 0; base < (uptr) arenas[i].pool_address; ++j, base += POOL_SIZE) { poolp p = (poolp)base; const uint sz = p->szidx; uint freeblocks; if (p->ref.count == 0) { / currently unused / assert(pool_is_in_list(p, arenas[i].freepools)); continue; } ++numpools[sz]; numblocks[sz] += p->ref.count; freeblocks = NUMBLOCKS(sz) - p->ref.count; numfreeblocks[sz] += freeblocks; #ifdef Py_DEBUG if (freeblocks > 0) assert(pool_is_in_list(p, usedpools[sz + sz])); #endif } } assert(narenas == narenas_currently_allocated); fputc('\n', out); fputs("class size num pools blocks in use avail blocks\n" "----- ---- --------- ------------- ------------\n", out); for (i = 0; i < numclasses; ++i) { size_t p = numpools[i]; size_t b = numblocks[i]; size_t f = numfreeblocks[i]; uint size = INDEX2SIZE(i); if (p == 0) { assert(b == 0 && f == 0); continue; } fprintf(out, "%5u %6u " "%11" PY_FORMAT_SIZE_T "u " "%15" PY_FORMAT_SIZE_T "u " "%13" PY_FORMAT_SIZE_T "u\n", i, size, p, b, f); allocated_bytes += b * size; available_bytes += f * size; pool_header_bytes += p * POOL_OVERHEAD; quantization += p * ((POOL_SIZE - POOL_OVERHEAD) % size); } fputc('\n', out); #ifdef PYMALLOC_DEBUG (void)printone(out, "# times object malloc called", serialno); #endif (void)printone(out, "# arenas allocated total", ntimes_arena_allocated); (void)printone(out, "# arenas reclaimed", ntimes_arena_allocated - narenas); (void)printone(out, "# arenas highwater mark", narenas_highwater); (void)printone(out, "# arenas allocated current", narenas); PyOS_snprintf(buf, sizeof(buf), "%" PY_FORMAT_SIZE_T "u arenas * %d bytes/arena", narenas, ARENA_SIZE); (void)printone(out, buf, narenas * ARENA_SIZE); fputc('\n', out); total = printone(out, "# bytes in allocated blocks", allocated_bytes); total += printone(out, "# bytes in available blocks", available_bytes); PyOS_snprintf(buf, sizeof(buf), "%u unused pools * %d bytes", numfreepools, POOL_SIZE); total += printone(out, buf, (size_t)numfreepools * POOL_SIZE); total += printone(out, "# bytes lost to pool headers", pool_header_bytes); total += printone(out, "# bytes lost to quantization", quantization); total += printone(out, "# bytes lost to arena alignment", arena_alignment); (void)printone(out, "Total", total); } #endif / #ifdef WITH_PYMALLOC / #ifdef Py_USING_MEMORY_DEBUGGER / Make this function last so gcc won't inline it since the definition is

} #endif