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

[Paul Jackson <pj@engr.sgi.com>]

Ingo wrote:
> 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.

Yes - agreed.  I should push in the direction of improving the
SN2 sched domain hierarchy.


Would be a good idea to rename 'cpu_distance()' to something more
specific, like 'cpu_dist_ndx()', and reserve the generic name
'cpu_distance()' for later use to return a scaled integer distance,
rather like 'node_distance()' does now.  For example, 'cpu_distance()'
might, someday, return integer values such as:

	40  217  252  253

as are displayed (in tenths) in the debug line:

---------------------
cacheflush times [4]: 4.0 (4080540) 21.7 (21781380) 25.2 (25259428) 25.3 (25372682)
---------------------

(that is, the integer (long)cost / 100000 - one less zero).

I don't know that we have any use, yet, for this 'cpu_distance()' as a
scaled integer value.  But I'd be more comfortable reserving that name
for that purpose.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@engr.sgi.com> 1.650.933.1373, 1.925.600.0401
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