Re: SLUB defrag pull request?

From: Christoph Lameter
Date: Thu Oct 23 2008 - 10:10:23 EST

On Thu, 23 Oct 2008, Pekka Enberg wrote:

On Thu, Oct 23, 2008 at 4:40 PM, Christoph Lameter
<cl@xxxxxxxxxxxxxxxxxxxx> wrote:
Solid? What is not solid? The SLUB design was made in part because of the
defrag problems that were not easy to solve with SLAB. The ability to lock
down a slab allows stabilizing objects. We discussed solutions to the
fragmentation problem for years and did not get anywhere with SLAB.

I'd assume he's talking about the Intel-reported regression that's yet
to be resolved.

On that subject:

Got a draft of a patch here that does freelist handling differently. Instead of building linked lists it uses free objects to build arrays of pointers to free objects. That improves cache cold free behavior since the object contents itself does not have to be touched on free.

The problem looks like its freeing objects on a different processor that where it was used last. With the pointer array it is only necessary to touch the objects that contain the arrays.
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