[Python-Dev] pymalloc killer (original) (raw)

Marangozov, Vladimir (Vladimir) vmarangozov@optimay.com
Wed, 3 Apr 2002 16:50:19 +0200

[Tim, in obmalloc.c]

_#define ADDRESSINRANGE(P, I) _ ((I) < narenas && (uptr)(P) - arenas[I] < (uptr)ARENASIZE)

Bravo! Very nice.

Now that the pool header is reduced in size by one slot, I can only suggest a small optimization to get rid off the multiplication when trying to extend the free list. Since you know the code by heart already, this should be self explanatory. It's only 3 lines of code:

  1. add a member in the pool struct, after capacity:

    uint lastoffset; /* free list tail block offset */

  2. In malloc, in the "try to extend the free list" block:

    size <<= ALIGNMENT_SHIFT; /* block size */ pool->lastoffset += size; pool->freeblock = (block *)pool + pool->lastoffset;

  3. In the "init_pool" block:

    pool->capacity = ... pool->lastoffset = POOL_OVERHEAD + size; UNLOCK();

In other words, the lastoffset acts as an upper bound watermark. I didn't want to do that optimization before, because it would have resulted in a bigger pool header and waste of space. Now it's ok.

Cheers, Vladimir