[PATCH v6 02/23] kconfig: Provide PREFERRED_CPU option

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Introduce a new config named PREFERRED_CPU.

This helps to:
- Avoid the code bloat when PREFERRED_CPU=n. In that cases preferred
  is same as active.
- Avoid the ifdeffery around PREFERRED_CPU in many files.

Since paravirtualized use case is the main driving force of this
feature, make it default for kernels with PARAVIRT=y

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 kernel/Kconfig.preempt | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 88c594c6d7fc..b3a543cb44cd 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -192,3 +192,17 @@ config SCHED_CLASS_EXT
 	  For more information:
 	    Documentation/scheduler/sched-ext.rst
 	    https://github.com/sched-ext/scx
+
+config PREFERRED_CPU
+	bool "Dynamic vCPU management based on steal time"
+	depends on PARAVIRT && SMP
+	default y
+	help
+	  This feature helps to reduce the steal time in paravirtualised
+	  environment, there by reducing vCPU preemption. Reducing vCPU
+	  preemption provides improved lock holder preemption and reduces
+	  cost of vCPU preemption in the host.
+
+	  By default preferred CPUs will be same as active CPUs. Depending
+	  on the steal time when steal_monitor driver is enabled,
+	  preferred CPUs could become subset of active CPUs.
-- 
2.47.3