Re: Major regression on hackbench with SLUB (more numbers)

Christoph Lameter
2007-12-13T22:22:29Z

On Tue, 11 Dec 2007, Ingo Molnar wrote:

> hackbench-10: 1.12 2.99 (166%)
> hackbench-20: 2.04 6.67 (226%)
> hackbench-50: 5.03 17.50 (247%)
>
> and hackbench overhead stands out, by a huge margin. Other stuff is
> within measurement noise. Neither SLUB nor SLAB debugging was turned on,
> all other debugging options were off too.

I just came back from vacation. The non linear growth of regression
indicates lock contention somewhere. Must be something special that was
triggered by hackbench.

We have had a regression like that in 2.6.24 before due to order 1 allocs
in the network layer. The .24 modifications for SLUB introduced page
allocator pass through for allocations > PAGESIZE/2. Order 1 allocs could
serialize on zone locks.