diff options
Diffstat (limited to 'Objects/obmalloc.c')
| -rw-r--r-- | Objects/obmalloc.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c index fc7bef6199..622da3ad08 100644 --- a/Objects/obmalloc.c +++ b/Objects/obmalloc.c @@ -1758,7 +1758,12 @@ pymalloc_free(void *ctx, void *p) /* 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(). + * the system free(). Except if this is the last + * arena in the list, keep it to avoid thrashing: + * keeping one wholly free arena in the list avoids + * pathological cases where a simple loop would + * otherwise provoke needing to allocate and free an + * arena on every iteration. See bpo-37257. * 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 @@ -1767,7 +1772,7 @@ pymalloc_free(void *ctx, void *p) * nfreepools. * 4. Else there's nothing more to do. */ - if (nf == ao->ntotalpools) { + if (nf == ao->ntotalpools && ao->nextarena != NULL) { /* Case 1. First unlink ao from usable_arenas. */ assert(ao->prevarena == NULL || |