[PATCH v2] cpusets: randomize node rotor used incpuset_mem_spread_node()

[Michal Hocko]

[I just realized that I forgot to CC mm mailing list]

On Fri 15-04-11 16:18:45, KOSAKI Motohiro wrote:
> Oops.
> I should have look into !mempolicy part too.
> I'm sorry.
> 
[...]
> Michal, I think this should be
> 
> #ifdef CONFIG_CPUSETS
> 	if (cpuset_do_page_mem_spread())
> 		p->cpuset_mem_spread_rotor = node_random(&p->mems_allowed);
> 	if (cpuset_do_slab_mem_spread())
> 		p->cpuset_slab_spread_rotor = node_random(&p->mems_allowed);
> #endif
> 
> because 99.999% people don't use cpuset's spread mem/slab feature and
> get_random_int() isn't zero cost.
> 
> What do you think?

You are right. I was thinking about lazy approach and initialize those
values when they are used for the first time. What about the patch
below?

Change from v1:
- initialize cpuset_{mem,slab}_spread_rotor lazily

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