A new attempt to fix the 1 CPU per node problem of the current NUMA
scheduler. The previous version was a bit too aggressive with cross
node balancing.
This patch:
- links the frequency of cross-node balances to the number of failed
local balance attempts while simplifying the code,
- 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, is a major issue on x86_64.
- 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.
Regards,
Erich