Charles-François Natali <neolo...@free.fr> added the comment:
> Hmm, quite slow indeed, are you sure you're not running in debug mode?
>
Well, yes, but it's no faster with a non-debug build: my laptop is
really crawling :-)
> If the performance regression is limited to read(), I don't think it's
> really an issue, but using mmap/munmap explicitly would probably benicer
> anyway (1° because it lets the glibc choose whatever heuristic is best,
> 2° because it would help release memory on more systems than just glibc
> systems). I think limiting ourselves to systems which have
> MMAP_ANONYMOUS is good enough.
>
Agreed.
Here's a patch.
----------
Added file: http://bugs.python.org/file23782/arenas_mmap.diff
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue11849>
_______________________________________
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -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 @@
/*
* 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 */
@@ -557,11 +560,6 @@
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);
if (arenaobj == NULL)
@@ -594,7 +592,12 @@
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 @@
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;
diff --git a/configure.in b/configure.in
--- a/configure.in
+++ b/configure.in
@@ -2567,8 +2567,8 @@
getgrouplist getgroups getlogin getloadavg getpeername getpgid getpid \
getpriority getresuid getresgid getpwent getspnam getspent getsid getwd \
if_nameindex \
- initgroups kill killpg lchmod lchown lockf linkat lstat lutimes memrchr \
- mbrtowc mkdirat mkfifo \
+ initgroups kill killpg lchmod lchown lockf linkat lstat lutimes mmap \
+ memrchr mbrtowc mkdirat mkfifo \
mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock
poll \
posix_fallocate posix_fadvise pread \
pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath
renameat \
@@ -2679,15 +2679,6 @@
[AC_MSG_RESULT(no)
])
-AC_MSG_CHECKING(whether mallopt can set malloc mmap threshold)
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-#include <malloc.h>
-]], [[mallopt(M_MMAP_THRESHOLD, 256 * 1024)]])],
- [AC_DEFINE(HAVE_MALLOPT_MMAP_THRESHOLD, 1, Define if mallopt can set malloc
mmap threshold.)
- AC_MSG_RESULT(yes)],
- [AC_MSG_RESULT(no)
-])
-
AC_MSG_CHECKING(for broken unsetenv)
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#include <stdlib.h>
diff --git a/pyconfig.h.in b/pyconfig.h.in
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -512,9 +512,6 @@
/* Define this if you have the makedev macro. */
#undef HAVE_MAKEDEV
-/* Define if mallopt can set malloc mmap threshold. */
-#undef HAVE_MALLOPT_MMAP_THRESHOLD
-
/* Define to 1 if you have the `mbrtowc' function. */
#undef HAVE_MBRTOWC
@@ -545,6 +542,9 @@
/* Define to 1 if you have the `mktime' function. */
#undef HAVE_MKTIME
+/* Define to 1 if you have the `mmap' function. */
+#undef HAVE_MMAP
+
/* Define to 1 if you have the `mremap' function. */
#undef HAVE_MREMAP
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