linux-kernel - [RFC][PATCH v1 1/3] x86/sched: Introduce arch_rebuild_sched

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Message-ID: <3567858.iIbC2pHGDl@kreacher>
Date: Thu, 25 Apr 2024 21:04:02 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: x86 Maintainers <x86@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux PM <linux-pm@...r.kernel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Ricardo Neri <ricardo.neri@...el.com>, Tim Chen <tim.c.chen@...el.com>
Subject: [RFC][PATCH v1 1/3] x86/sched: Introduce arch_rebuild_sched_domains()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Add arch_rebuild_sched_domains() for rebuilding scheduling domains and
updating topology on x86 and make the ITMT code use it.

First of all, this reduces code duplication somewhat and eliminates
a need to use an extern variable, but it will also lay the ground for
future work related to CPU capacity scaling.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 arch/x86/include/asm/topology.h |    6 ++++--
 arch/x86/kernel/itmt.c          |   12 ++++--------
 arch/x86/kernel/smpboot.c       |   10 +++++++++-
 3 files changed, 17 insertions(+), 11 deletions(-)

Index: linux-pm/arch/x86/include/asm/topology.h
===================================================================
--- linux-pm.orig/arch/x86/include/asm/topology.h
+++ linux-pm/arch/x86/include/asm/topology.h
@@ -235,8 +235,6 @@ struct pci_bus;
 int x86_pci_root_bus_node(int bus);
 void x86_pci_root_bus_resources(int bus, struct list_head *resources);
 
-extern bool x86_topology_update;
-
 #ifdef CONFIG_SCHED_MC_PRIO
 #include <asm/percpu.h>
 
@@ -284,9 +282,13 @@ static inline long arch_scale_freq_capac
 
 extern void arch_set_max_freq_ratio(bool turbo_disabled);
 extern void freq_invariance_set_perf_ratio(u64 ratio, bool turbo_disabled);
+
+void arch_rebuild_sched_domains(void);
 #else
 static inline void arch_set_max_freq_ratio(bool turbo_disabled) { }
 static inline void freq_invariance_set_perf_ratio(u64 ratio, bool turbo_disabled) { }
+
+static inline void arch_rebuild_sched_domains(void) { }
 #endif
 
 extern void arch_scale_freq_tick(void);
Index: linux-pm/arch/x86/kernel/itmt.c
===================================================================
--- linux-pm.orig/arch/x86/kernel/itmt.c
+++ linux-pm/arch/x86/kernel/itmt.c
@@ -54,10 +54,8 @@ static int sched_itmt_update_handler(str
 	old_sysctl = sysctl_sched_itmt_enabled;
 	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 
-	if (!ret && write && old_sysctl != sysctl_sched_itmt_enabled) {
-		x86_topology_update = true;
-		rebuild_sched_domains();
-	}
+	if (!ret && write && old_sysctl != sysctl_sched_itmt_enabled)
+		arch_rebuild_sched_domains();
 
 	mutex_unlock(&itmt_update_mutex);
 
@@ -114,8 +112,7 @@ int sched_set_itmt_support(void)
 
 	sysctl_sched_itmt_enabled = 1;
 
-	x86_topology_update = true;
-	rebuild_sched_domains();
+	arch_rebuild_sched_domains();
 
 	mutex_unlock(&itmt_update_mutex);
 
@@ -150,8 +147,7 @@ void sched_clear_itmt_support(void)
 	if (sysctl_sched_itmt_enabled) {
 		/* disable sched_itmt if we are no longer ITMT capable */
 		sysctl_sched_itmt_enabled = 0;
-		x86_topology_update = true;
-		rebuild_sched_domains();
+		arch_rebuild_sched_domains();
 	}
 
 	mutex_unlock(&itmt_update_mutex);
Index: linux-pm/arch/x86/kernel/smpboot.c
===================================================================
--- linux-pm.orig/arch/x86/kernel/smpboot.c
+++ linux-pm/arch/x86/kernel/smpboot.c
@@ -39,6 +39,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/cpuset.h>
 #include <linux/init.h>
 #include <linux/smp.h>
 #include <linux/export.h>
@@ -125,7 +126,7 @@ static DEFINE_PER_CPU_ALIGNED(struct mwa
 int __read_mostly __max_smt_threads = 1;
 
 /* Flag to indicate if a complete sched domain rebuild is required */
-bool x86_topology_update;
+static bool x86_topology_update;
 
 int arch_update_cpu_topology(void)
 {
@@ -135,6 +136,13 @@ int arch_update_cpu_topology(void)
 	return retval;
 }
 
+#ifdef CONFIG_X86_64
+void arch_rebuild_sched_domains(void) {
+	x86_topology_update = true;
+	rebuild_sched_domains();
+}
+#endif
+
 static unsigned int smpboot_warm_reset_vector_count;
 
 static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)