PyObject_Calloc(), _PyObject_GC_Calloc(). bytes(int) and bytearray(int) are now
using ``calloc()`` instead of ``malloc()`` for large objects which is faster
and use less memory (until the bytearray buffer is filled with data).
Add new enum:
* PyMemAllocatorDomain
Add new structures:
* PyMemAllocator
* PyObjectArenaAllocator
Add new functions:
* PyMem_RawMalloc(), PyMem_RawRealloc(), PyMem_RawFree()
* PyMem_GetAllocator(), PyMem_SetAllocator()
* PyObject_GetArenaAllocator(), PyObject_SetArenaAllocator()
* PyMem_SetupDebugHooks()
Changes:
* PyMem_Malloc()/PyObject_Realloc() now always call malloc()/realloc(), instead
of calling PyObject_Malloc()/PyObject_Realloc() in debug mode.
* PyObject_Malloc()/PyObject_Realloc() now falls back to
PyMem_Malloc()/PyMem_Realloc() for allocations larger than 512 bytes.
* Redesign debug checks on memory block allocators as hooks, instead of using C
macros
* Add a new PyMemAllocators structure
* New functions:
- PyMem_RawMalloc(), PyMem_RawRealloc(), PyMem_RawFree(): GIL-free memory
allocator functions
- PyMem_GetRawAllocators(), PyMem_SetRawAllocators()
- PyMem_GetAllocators(), PyMem_SetAllocators()
- PyMem_SetupDebugHooks()
- _PyObject_GetArenaAllocators(), _PyObject_SetArenaAllocators()
* Add unit test for PyMem_Malloc(0) and PyObject_Malloc(0)
* Add unit test for new get/set allocators functions
* PyObject_Malloc() now falls back on PyMem_Malloc() instead of malloc() if
size is bigger than SMALL_REQUEST_THRESHOLD, and PyObject_Realloc() falls
back on PyMem_Realloc() instead of realloc()
* PyMem_Malloc() and PyMem_Realloc() now always call malloc() and realloc(),
instead of calling PyObject_Malloc() and PyObject_Realloc() in debug mode
longer required as of Python 2.5+ when the gc_refs changed from an int (4
bytes) to a Py_ssize_t (8 bytes) as the minimum size is 16 bytes.
The use of a 'long double' triggered a warning by Clang trunk's
Undefined-Behavior Sanitizer as on many platforms a long double requires
16-byte alignment but the Python memory allocator only guarantees 8 byte
alignment.
So our code would allocate and use these structures with technically improper
alignment. Though it didn't matter since the 'dummy' field is never used.
This silences that warning.
Spelunking into code history, the double was added in 2001 to force better
alignment on some platforms and changed to a long double in 2002 to appease
Tru64. That issue should no loner be present since the upgrade from int to
Py_ssize_t where the minimum structure size increased to 16 (unless anyone
knows of a platform where ssize_t is 4 bytes?) or 24 bytes depending on if the
build uses 4 or 8 byte pointers.
We can probably get rid of the double and this union hack all together today.
That is a slightly more invasive change that can be left for later.
A more correct non-hacky alternative if any alignment issues are still found
would be to use a compiler specific alignment declaration on the structure and
determine which value to use at configure time.
svn+ssh://pythondev@svn.python.org/python/trunk
........
r70546 | antoine.pitrou | 2009-03-23 19:41:45 +0100 (lun., 23 mars 2009) | 9 lines
Issue #4688: Add a heuristic so that tuples and dicts containing only
untrackable objects are not tracked by the garbage collector. This can
reduce the size of collections and therefore the garbage collection overhead
on long-running programs, depending on their particular use of datatypes.
(trivia: this makes the "binary_trees" benchmark from the Computer Language
Shootout 40% faster)
........
variations of the type struct and its attachments. In Py3k, all type
structs have to have all fields -- no binary backwards compatibility.
Had to change the complex object to a new-style number!
number of tests, all because of the codecs/_multibytecodecs issue described
here (it's not a Py3K issue, just something Py3K discovers):
http://mail.python.org/pipermail/python-dev/2006-April/064051.html
Hye-Shik Chang promised to look for a fix, so no need to fix it here. The
tests that are expected to break are:
test_codecencodings_cn
test_codecencodings_hk
test_codecencodings_jp
test_codecencodings_kr
test_codecencodings_tw
test_codecs
test_multibytecodec
This merge fixes an actual test failure (test_weakref) in this branch,
though, so I believe merging is the right thing to do anyway.
This was mostly a matter of adding comments and light code rearrangement.
Upon untracking, gc_next is still set to NULL. It's a cheap way to
provoke memory faults if calling code is insane. It's also used in some
way by the trashcan mechanism.
object should now have a well-defined gc_refs value, with clear transitions
among gc_refs states. As a result, none of the visit_XYZ traversal
callbacks need to check IS_TRACKED() anymore, and those tests were removed.
(They were already looking for objects with specific gc_refs states, and
the gc_refs state of an untracked object can no longer match any other
gc_refs state by accident.)
Added more asserts.
I expect that the gc_next == NULL indicator for an untracked object is
now redundant and can also be removed, but I ran out of time for this.
As threatened, PyMem_{Free, FREE} also invoke the object deallocator now
when pymalloc is enabled (well, it does when pymalloc isn't enabled too,
but in that case "the object deallocator" is plain free()).
This is maximally backward-compatible, but it leaves a bitter aftertaste.
Also massive reworking of comments.
Added code to call this when PYMALLOC_DEBUG is enabled, and envar
PYTHONMALLOCSTATS is set, whenever a new arena is obtained and once
late in the Python shutdown process.
it's enabled.
Allow PyObject_Del, PyObject_Free, and PyObject_GC_Del to be used as
function designators. Provide source compatibility macros.
Make PyObject_GC_Track and PyObject_GC_UnTrack functions instead of
trivial macros wrapping functions.
and not pymalloc. Add the functions PyMalloc_New, PyMalloc_NewVar, and
PyMalloc_Del that will use pymalloc if it's enabled. If pymalloc is
not enabled then they use the standard malloc (PyMem_*).
alignment gimmick. David Abrahams notes that the standard "long double"
actually requires stricter alignment than "double" on some Tru64 box.
On my box and yours <wink>, it's the same, so no harm done on most
boxes.
The platform requires 8-byte alignment for doubles, but the GC header
was 12 bytes and that threw off the natural alignment of the double
members of a subtype of complex. The fix puts the GC header into a
union with a double as the other member, to force no-looser-than
double alignment of GC headers. On boxes that require 8-byte alignment
for doubles, this may add pad bytes to the GC header accordingly; ditto
for platforms that *prefer* 8-byte alignment for doubles. On platforms
that don't care, it shouldn't change the memory layout (because the
size of the old GC header is certainly greater than the size of a double
on all platforms, so unioning with a double shouldn't change size or
alignment on such boxes).
This simplifies the rounding in _PyObject_VAR_SIZE, allows to restore the
pre-rounding calling sequence, and allows some nice little simplifications
in its callers. I'm still making it return a size_t, though.
As Guido suggested, this makes the new subclassing code substantially
simpler. But the mechanics of doing it w/ C macro semantics are a mess,
and _PyObject_VAR_SIZE has a new calling sequence now.
Question: The PyObject_NEW_VAR macro appears to be part of the public API.
Regardless of what it expands to, the notion that it has to round up the
memory it allocates is new, and extensions containing the old
PyObject_NEW_VAR macro expansion (which was embedded in the
PyObject_NEW_VAR expansion) won't do this rounding. But the rounding
isn't actually *needed* except for new-style instances with dict pointers
after a variable-length blob of embedded data. So my guess is that we do
not need to bump the API version for this (as the rounding isn't needed
for anything an extension can do unless it's recompiled anyway). What's
your guess?
pad memory to properly align the __dict__ pointer in all cases.
gcmodule.c/objimpl.h, _PyObject_GC_Malloc:
+ Added a "padding" argument so that this flavor of malloc can allocate
enough bytes for alignment padding (it can't know this is needed, but
its callers do).
typeobject.c, PyType_GenericAlloc:
+ Allocated enough bytes to align the __dict__ pointer.
+ Sped and simplified the round-up-to-PTRSIZE logic.
+ Added blank lines so I could parse the if/else blocks <0.7 wink>.
Victor Stinner
Benjamin Peterson
Serhiy Storchaka
Antoine Pitrou
Gregory P. Smith
David Malcolm
Martin v. Löwis
Kristján Valur Jónsson
Christian Heimes
Neal Norwitz
Guido van Rossum
Thomas Wouters
Barry Warsaw
Georg Brandl
Tim Peters
Jim Fulton
Mark Hammond
Neil Schemenauer