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Revert "bpo-40521: Remove freelist from collections.deque() (GH-21073)" (GH-24944)

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This reverts commit 32f2eda859.
It can be re-applied if the subinterpreter PEP is approved.
Otherwise, the commit degraded performance with no offsetting
benefit.
This commit is contained in:
Raymond Hettinger 2021-03-25 13:32:23 -07:00 • committed by GitHub
parent 929c9039fe
commit 3bb19873ab
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 21 additions and 2 deletions
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23
Modules/_collectionsmodule.c
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@ -118,9 +118,23 @@ static PyTypeObject deque_type;
#define CHECK_NOT_END(link)
#endif
/* A simple freelisting scheme is used to minimize calls to the memory
allocator. It accommodates common use cases where new blocks are being
added at about the same rate as old blocks are being freed.
*/
#define MAXFREEBLOCKS 16
static Py_ssize_t numfreeblocks = 0;
static block *freeblocks[MAXFREEBLOCKS];
static block *
newblock(void) {
block *b = PyMem_Malloc(sizeof(block));
block *b;
if (numfreeblocks) {
numfreeblocks--;
return freeblocks[numfreeblocks];
}
b = PyMem_Malloc(sizeof(block));
if (b != NULL) {
return b;
}
@ -131,7 +145,12 @@ newblock(void) {
static void
freeblock(block *b)
{
PyMem_Free(b);
if (numfreeblocks < MAXFREEBLOCKS) {
freeblocks[numfreeblocks] = b;
numfreeblocks++;
} else {
PyMem_Free(b);
}
}
static PyObject *