Re: [RFC PATCH v3 1/3] sched: schedule balance map foundation

[Alex Shi]

On 02/22/2013 12:19 PM, Michael Wang wrote:
> 
>> > Why not seek other way to change O(n^2) to O(n)?
>> > 
>> > Access 2G memory is unbelievable performance cost.
> Not access 2G memory, but (2G / 16K) memory, the sbm size is O(N).
> 
> And please notice that on 16k cpus system, topology will be deep if NUMA
> enabled (O(log N) as Peter said), and that's really a good stage for
> this idea to perform on, we could save lot's of recursed 'for' cycles.
> 

CPU execute part is very very fast compare to the memory access, the
'for' cycles cost is most on the memory access for many domain/groups
data, not instruction execution.

In a hot patch, several KB memory access will cause clear cpu cache
pollution then make kernel slowly.

-- 
Thanks Alex
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