On Thu, Aug 28, 2025 at 08:13:51PM +0530, Shrikanth Hegde wrote:

quoted

--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -170,6 +170,9 @@ config PPC
  	select ARCH_STACKWALK
  	select ARCH_SUPPORTS_ATOMIC_RMW
  	select ARCH_SUPPORTS_DEBUG_PAGEALLOC	if PPC_BOOK3S || PPC_8xx
+	select ARCH_SUPPORTS_SCHED_SMT		if PPC64 && SMP
+	select ARCH_SUPPORTS_SCHED_MC		if PPC64 && SMP
+	select SCHED_MC				if ARCH_SUPPORTS_SCHED_MC

Wondering if this SCHED_MC is necessary here? shouldn't it be set by arch/Kconfig?

Ah, so without this SCHED_MC becomes a user selectable option, with this
it is an always on option (for ppc64) -- no user prompt.

That is, this is the only way I found to have similar semantics to this:

quoted

-config SCHED_MC
-	def_bool y
-	depends on PPC64 && SMP
-

Which is also not a user selectable option.

nit: Also, can we have so they are still sorted?
	select ARCH_SUPPORTS_SCHED_MC		if PPC64 && SMP
	select ARCH_SUPPORTS_SCHED_SMT		if PPC64 && SMP

Sure, let me flip them. I need to prod that that patch anyway, built
robot still ain'ted happy.

quoted

--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig

@@ -547,15 +547,11 @@ config NODES_SHIFT
  	depends on NUMA
  	default "1"
-config SCHED_SMT
-	def_bool n
-
-config SCHED_MC
-	def_bool n
-
  config SCHED_TOPOLOGY
  	def_bool y
  	prompt "Topology scheduler support"
+	select ARCH_SUPPORTS_SCHED_SMT
+	select ARCH_SUPPORTS_SCHED_MC
  	select SCHED_SMT
  	select SCHED_MC

Same here. Above two are needed?

Same issue; previously neither were user selectable symbols. By only
selecting the ARCH_SUPPORTS_$FOO variants, the $FOO options become user
selectable. By then explicitly selecting $FOO as well, that user option
is taken away again.

quoted

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -330,6 +330,10 @@ config X86
  	imply IMA_SECURE_AND_OR_TRUSTED_BOOT    if EFI
  	select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
  	select ARCH_SUPPORTS_PT_RECLAIM		if X86_64
+	select ARCH_SUPPORTS_SCHED_SMT		if SMP
+	select SCHED_SMT			if SMP

Is this SCHED_SMT needed here?

Same again...

quoted

+	select ARCH_SUPPORTS_SCHED_CLUSTER	if SMP
+	select ARCH_SUPPORTS_SCHED_MC		if SMP
  config INSTRUCTION_DECODER
  	def_bool y

@@ -1036,29 +1040,6 @@ config NR_CPUS
  	  This is purely to save memory: each supported CPU adds about 8KB
  	  to the kernel image.
-config SCHED_CLUSTER
-	bool "Cluster scheduler support"
-	depends on SMP
-	default y
-	help
-	  Cluster scheduler support improves the CPU scheduler's decision
-	  making when dealing with machines that have clusters of CPUs.
-	  Cluster usually means a couple of CPUs which are placed closely
-	  by sharing mid-level caches, last-level cache tags or internal
-	  busses.
-
-config SCHED_SMT
-	def_bool y if SMP
-
-config SCHED_MC
-	def_bool y
-	prompt "Multi-core scheduler support"
-	depends on SMP
-	help
-	  Multi-core scheduler support improves the CPU scheduler's decision
-	  making when dealing with multi-core CPU chips at a cost of slightly
-	  increased overhead in some places. If unsure say N here.

See how SCHED_SMT is not a user option for x86.