Re: [patch] sched: auto-tune migration costs [was: Re: Industry db benchmark result on recent 2.6 kernels]

[Ingo Molnar <mingo@elte.hu>]

* Paul Jackson <pj@engr.sgi.com> wrote:

> 
>  3) I was noticing that my test system was only showing a couple of 
>     distinct values for cpu_distance, even though it has 4 distinct 
>     distances for values of node_distance.  So I coded up a variant of 
>     cpu_distance that converts the problem to a node_distance problem, 
>     and got the following cost matrix:

>     The code (below) is twice as complicated, the runtime twice as long,
>     and it's less intuitive - sched_domains seems more appropriate as
>     the basis for migration costs than the node distances in SLIT tables.
>     Finally, I don't know if distinguishing between costs of 21.7 and
>     25.3 is worth much.

the main problem is that we can do nothing with this matrix: we only 
print it, but then the values get written into a 0/1 sched-domains 
hierarchy - so the information is lost.

if you create a sched-domains hierarchy (based on the SLIT tables, or in 
whatever other way) that matches the CPU hierarchy then you'll 
automatically get the proper distances detected.

	Ingo