Re: [PATCH 0/6] fs: Scalability of sockets/pipes allocation/deallocationon SMP

[Christoph Lameter]

On Thu, 27 Nov 2008, Eric Dumazet wrote:

> with slub_min_objects=45 :
>
> # cat /sys/kernel/slab/filp/order
> 2
> # time ./socket8
> real    0m1.652s
> user    0m0.694s
> sys     0m12.367s

That may be a good value. How many processor do you have? Look at
calculate_order() in mm/slub.c:

   if (!min_objects)
                min_objects = 4 * (fls(nr_cpu_ids) + 1);

We couild increase the scaling factor there or start
with a mininum of 20 objects?


Try

	min_objects = 20 + 4 * (fls(nr_cpu_ids) + 1);

> I would say slub_min_objects=45 is the optimal value on 32bit arches to
> get acceptable performance on this workload (order=2 for filp kmem_cache)
>
> Note : SLAB here is disastrous, but you already knew that :)

Its good though to have examples where the queue management gets in the
way of performance.
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