mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-04 00:48:58 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 8

Better resolution for issue #11849: Ensure that free()d memory arenas are really released

Browse source 
on POSIX systems supporting anonymous memory mappings.  Patch by Charles-François Natali.
This commit is contained in:
Antoine Pitrou 2011-11-26 01:11:02 +01:00
parent 61ea8a0d28
commit f0effe6379
5 changed files with 35 additions and 65 deletions
Download patch file Download diff file Expand all files Collapse all files

37
Objects/obmalloc.c
View file

@ -2,8 +2,11 @@
#ifdef WITH_PYMALLOC
#ifdef HAVE_MALLOPT_MMAP_THRESHOLD
#include <malloc.h>
#ifdef HAVE_MMAP
#include <sys/mman.h>
#ifdef MAP_ANONYMOUS
#define ARENAS_USE_MMAP
#endif
#endif
#ifdef WITH_VALGRIND
@ -183,15 +186,15 @@ static int running_on_valgrind = -1;
/*
* The allocator sub-allocates <Big> blocks of memory (called arenas) aligned
* on a page boundary. This is a reserved virtual address space for the
* current process (obtained through a malloc call). In no way this means
* that the memory arenas will be used entirely. A malloc(<Big>) is usually
* an address range reservation for <Big> bytes, unless all pages within this
* space are referenced subsequently. So malloc'ing big blocks and not using
* them does not mean "wasting memory". It's an addressable range wastage...
* current process (obtained through a malloc()/mmap() call). In no way this
* means that the memory arenas will be used entirely. A malloc(<Big>) is
* usually an address range reservation for <Big> bytes, unless all pages within
* this space are referenced subsequently. So malloc'ing big blocks and not
* using them does not mean "wasting memory". It's an addressable range
* wastage...
*
* Therefore, allocating arenas with malloc is not optimal, because there is
* some address space wastage, but this is the most portable way to request
* memory from the system across various platforms.
* Arenas are allocated with mmap() on systems supporting anonymous memory
* mappings to reduce heap fragmentation.
*/
#define ARENA_SIZE (256 << 10) /* 256KB */
@ -556,11 +559,6 @@ new_arena(void)
#if SIZEOF_SIZE_T <= SIZEOF_INT
if (numarenas > PY_SIZE_MAX / sizeof(*arenas))
return NULL; /* overflow */
#endif
#ifdef HAVE_MALLOPT_MMAP_THRESHOLD
/* Ensure arenas are allocated by mmap to avoid heap fragmentation. */
if (numarenas == INITIAL_ARENA_OBJECTS)
mallopt(M_MMAP_THRESHOLD, ARENA_SIZE);
#endif
nbytes = numarenas * sizeof(*arenas);
arenaobj = (struct arena_object *)realloc(arenas, nbytes);
@ -594,7 +592,12 @@ new_arena(void)
arenaobj = unused_arena_objects;
unused_arena_objects = arenaobj->nextarena;
assert(arenaobj->address == 0);
#ifdef ARENAS_USE_MMAP
arenaobj->address = (uptr)mmap(NULL, ARENA_SIZE, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
#else
arenaobj->address = (uptr)malloc(ARENA_SIZE);
#endif
if (arenaobj->address == 0) {
/* The allocation failed: return NULL after putting the
* arenaobj back.
@ -1071,7 +1074,11 @@ PyObject_Free(void *p)
unused_arena_objects = ao;
/* Free the entire arena. */
#ifdef ARENAS_USE_MMAP
munmap((void *)ao->address, ARENA_SIZE);
#else
free((void *)ao->address);
#endif
ao->address = 0; /* mark unassociated */
--narenas_currently_allocated;