Re: [PATCHSET x86/core/percpu] improve the first percpu chunk allocation

[Tejun Heo]

Hello, Ingo.

Ingo Molnar wrote:
> * Tejun Heo <tj@xxxxxxxxxx> wrote:
> 
>>> and i think that abstraction is wrong.
>> No, it's not wrong.  It simply is irrelevant - it's congruent 
>> vs. contiguos and all that we need is congruent.  Contiguous 
>> of course achieves congruent but it doesn't make any 
>> difference for this purpose.
> 
> Well, as long as we can go up in unit size to 2MB (on 64-bit 
> x86) i'm fine with that model.

Yeap, it defintely can.

> There's no granularity artifacts, right? pcpu_populate_chunk() 
> intelligently only populates pages on an as-needed basis, so 
> extending the percpu areas with a 2MB unit does not trigger 
> nr_cpus*2MB allocations straight away.

Yeap, it doesn't although reclamation is done per-chunk currently.

> The code looks very clean and if we can agree on the SMP/NUMA 
> symmetry and the dynamic-ptr optimizations that it allows, plus 
> if you can up the unit size to 2MB on 64-bit x86, i'm a happy 
> camper and will pull it.

Sounds good.  Thanks.

-- 
tejun
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