Avoid needlessly costly migrations. CONFIG_SCHED_CPU_AFFINITY

Given a choice between several available CPUs (unlinked) on which
to schedule a task, let the scheduler select the CPU closest to
where that task was previously scheduled.  Hopefully, this will
reduce cache migration penalties.

Notes: SCHED_CPU_AFFINITY is dependent upon x86 (only x86 is
supported at this time). Also PFair/PD^2 does not make use of
this feature.

Signed-off-by: Andrea Bastoni <bastoni@cs.unc.edu>

1 files changed, 19 insertions, 0 deletions

diff --git a/litmus/Kconfig b/litmus/Kconfig
index ad8dc8308cf0..d7fde6f97e14 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -62,6 +62,25 @@ config LITMUS_LOCKING
 
 endmenu
 
+menu "Performance Enhancements"
+
+config SCHED_CPU_AFFINITY
+        bool "Local Migration Affinity"
+        depends on X86
+        default y
+        help
+          Rescheduled tasks prefer CPUs near to their previously used CPU.  This
+          may improve performance through possible preservation of cache affinity.
+
+          Warning: May make bugs harder to find since tasks may migrate less often.
+
+          NOTES:
+                * Feature is not utilized by PFair/PD^2.
+
+          Say Yes if unsure.
+
+endmenu
+
 menu "Tracing"
 
 config FEATHER_TRACE