Re: [patch 2.6.0t4] 1 cpu/node scheduler fix

["Martin J. Bligh" <mbligh@aracnet.com>]

> This is the 1 cpu/node fix of the NUMA scheduler rewritten for the new
> cpumask handling. The previous version was a bit too aggressive with
> cross node balancing so I changed the default timings a bit such that
> the behavior is very similar to the old one.
> 
> Here is what the patch does:
> - Links the frequency of cross-node balances to the number of failed
> local balance attempts. This simplifies the code by removing the too
> rigid cross-node balancing dependency of the timer interrupts.
> 
> - Fixes the 1 CPU/node issue, i.e. eliminates local balance attempts
> for the nodes which have only one CPU. Can happen on any NUMA
> platform (playing around with a 2 CPU/node box and have a flaky CPU,
> so I have sometimes a node with only one CPU), is a major issue on
> AMD64.
> 
> - Makes the cross-node balance frequency tunable by the parameter
> NUMA_FACTOR_BONUS. Its default setting is such that the scheduler
> behaves like before: cross node balance every 5 local node balances on
> an idle CPU, every 2 local node balances on a busy CPU. This parameter
> should be tuned for each platform depending on its NUMA factor.

This seems to clear up the low end stuff I was seeing before - thanks.

Did you (or anyone else) get a chance to test this on AMD? Would
be nice to confirm that's fixed ...

M.