1 files changed, 43 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index dd0bfc291a68..fe11fccf7e41 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -856,6 +856,49 @@ running once the system is up.
 
         mga=            [HW,DRM]
 
+        migration_cost=
+                        [KNL,SMP] debug: override scheduler migration costs
+                        Format: <level-1-usecs>,<level-2-usecs>,...
+                        This debugging option can be used to override the
+                        default scheduler migration cost matrix. The numbers
+                        are indexed by 'CPU domain distance'.
+                        E.g. migration_cost=1000,2000,3000 on an SMT NUMA
+                        box will set up an intra-core migration cost of
+                        1 msec, an inter-core migration cost of 2 msecs,
+                        and an inter-node migration cost of 3 msecs.
+
+                        WARNING: using the wrong values here can break
+                        scheduler performance, so it's only for scheduler
+                        development purposes, not production environments.
+
+        migration_debug=
+                        [KNL,SMP] migration cost auto-detect verbosity
+                        Format=<0|1|2>
+                        If a system's migration matrix reported at bootup
+                        seems erroneous then this option can be used to
+                        increase verbosity of the detection process.
+                        We default to 0 (no extra messages), 1 will print
+                        some more information, and 2 will be really
+                        verbose (probably only useful if you also have a
+                        serial console attached to the system).
+
+        migration_factor=
+                        [KNL,SMP] multiply/divide migration costs by a factor
+                        Format=<percent>
+                        This debug option can be used to proportionally
+                        increase or decrease the auto-detected migration
+                        costs for all entries of the migration matrix.
+                        E.g. migration_factor=150 will increase migration
+                        costs by 50%. (and thus the scheduler will be less
+                        eager migrating cache-hot tasks)
+                        migration_factor=80 will decrease migration costs
+                        by 20%. (thus the scheduler will be more eager to
+                        migrate tasks)
+
+                        WARNING: using the wrong values here can break
+                        scheduler performance, so it's only for scheduler
+                        development purposes, not production environments.
+
         mousedev.tap_time=
                         [MOUSE] Maximum time between finger touching and
                         leaving touchpad surface for touch to be considered