Re: [PATCH v4 00/22] slab: replace cpu (partial) slabs with sheaves

Vlastimil Babka
2026-02-06T16:44:48Z

On 2/4/26 19:24, Christoph Lameter (Ampere) wrote:
> On Wed, 4 Feb 2026, Vlastimil Babka wrote:
>
>> > So I think the performance of the percpu partial list and the sheaves mechanism
>> > is roughly the same, which is consistent with our expectations.
>>
>> Thanks!
>
> There are other considerations that usually do not show up well in
> benchmark tests.
>
> The sheaves cannot do the spatial optimizations that cpu partial lists
> provide. Fragmentation in slab caches (and therefore the nubmer of
> partial slab pages) will increase since
>
> 1. The objects are not immediately returned to their slab pages but end up
> in some queuing structure.
>
> 2. Available objects from a single slab page are not allocated in sequence
> to empty partial pages and remove the page from the partial lists.
>
> Objects are put into some queue on free and are processed on a FIFO basis.
> Objects allocated may come from lots of different slab pages potentially
> increasing TLB pressure.

IIUC this is what you said before [1] and the cover letter has a link and a
summary of it.

[1] https://lore.kernel.org/all/f7c33974-e520-387e-9e2f-1e523bfe1545@gentwo.org/