[PATCH v6 0/2] Adjust NUMA imbalance for multiple LLCs

[Mel Gorman <mgorman@techsingularity.net>]

Changelog sinve v5
o Fix off-by-one error

Changelog since V4
o Scale imbalance based on the top domain that prefers siblings
o Keep allowed imbalance as 2 up to the point where LLCs can be overloaded

Changelog since V3
o Calculate imb_numa_nr for multiple SD_NUMA domains
o Restore behaviour where communicating pairs remain on the same node

Commit 7d2b5dd0bcc4 ("sched/numa: Allow a floating imbalance between NUMA
nodes") allowed an imbalance between NUMA nodes such that communicating
tasks would not be pulled apart by the load balancer. This works fine when
there is a 1:1 relationship between LLC and node but can be suboptimal
for multiple LLCs if independent tasks prematurely use CPUs sharing cache.

The series addresses two problems -- inconsistent logic when allowing a
NUMA imbalance and sub-optimal performance when there are many LLCs per
NUMA node.

 include/linux/sched/topology.h |  1 +
 kernel/sched/fair.c            | 30 ++++++++++---------
 kernel/sched/topology.c        | 53 ++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+), 13 deletions(-)

-- 
2.31.1