Re: Mainline kernel OLTP performance update

On Fri, 2009-01-23 at 10:22 -0500, Christoph Lameter wrote:

On Fri, 23 Jan 2009, Pekka Enberg wrote:

quoted

Looking at __slab_free(), unless page->inuse is constantly zero and we
discard the slab, it really is just cache effects (10% sounds like a
lot, though!). AFAICT, the only way to optimize that is with Christoph's
unfinished pointer freelists patches or with a remote free list like in
SLQB.

No there is another way. Increase the allocator order to 3 for the
kmalloc-8192 slab then multiple 8k blocks can be allocated from one of the
larger chunks of data gotten from the page allocator. That will allow slub
to do fast allocs.

I wonder why that doesn't happen already, actually. The slub_max_order
know is capped to PAGE_ALLOC_COSTLY_ORDER ("3") by default and obviously
order 3 should be as good fit as order 2 so 'fraction' can't be too high
either. Hmm.

		Pekka