[PATCH v4 18/24] sched/task_struct: Add helpers for IPC classification

[Ricardo Neri]

The raw classification that hardware provides for a task may not
be directly usable by the scheduler: the classification may change too
frequently or architecture-specific implementations may need to consider
additional factors. For instance, some processors with Intel Thread
Director need to consider the state of the SMT siblings of a core.

Provide per-task helper variables that architectures can use to
postprocess the classification that hardware provides.

Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Ionela Voinescu <ionela.voinescu@xxxxxxx>
Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
Cc: Lukasz Luba <lukasz.luba@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Perry Yuan <Perry.Yuan@xxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Tim C. Chen <tim.c.chen@xxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Zhao Liu <zhao1.liu@xxxxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
---
Changes since v3:
 * None

Changes since v2:
 * None

Changes since v1:
 * Used bit-fields to fit all the IPC class data in 4 bytes. (PeterZ)
 * Shortened names of the helpers.
 * Renamed helpers with the ipcc_ prefix.
 * Reworded commit message for clarity
---
 include/linux/sched.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0e1c38ad09c2..719147460ca8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1541,7 +1541,17 @@ struct task_struct {
 	 * A hardware-defined classification of task that reflects but is
 	 * not identical to the number of instructions per cycle.
 	 */
-	unsigned short			ipcc;
+	unsigned int			ipcc : 9;
+	/*
+	 * A candidate classification that arch-specific implementations
+	 * qualify for correctness.
+	 */
+	unsigned int			ipcc_tmp : 9;
+	/*
+	 * Counter to filter out transient candidate classifications
+	 * of a task.
+	 */
+	unsigned int			ipcc_cntr : 14;
 #endif
 
 	/*
-- 
2.25.1