linux-kernel - [GIT pull] sched/urgent for v5.16-rc5

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Date:   Sun, 12 Dec 2021 11:34:22 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] sched/urgent for v5.16-rc5

Linus,

please pull the latest sched/urgent branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-2021-12-12

up to:  cabdc3a8475b: sched,x86: Don't use cluster topology for x86 hybrid CPUs


A single fix for the x86 scheduler topology:

  Using cluster topology on hybrid CPUs, e.g. Alder Lake, biases the
  scheduler towards the ATOM cluster as that has more total capacity.
  Use selection based on CPU priority instead.

Thanks,

	tglx

------------------>
Peter Zijlstra (1):
      sched,x86: Don't use cluster topology for x86 hybrid CPUs


 arch/x86/kernel/smpboot.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ac2909f0cab3..617012f4619f 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -579,6 +579,17 @@ static struct sched_domain_topology_level x86_numa_in_package_topology[] = {
 	{ NULL, },
 };
 
+static struct sched_domain_topology_level x86_hybrid_topology[] = {
+#ifdef CONFIG_SCHED_SMT
+	{ cpu_smt_mask, x86_smt_flags, SD_INIT_NAME(SMT) },
+#endif
+#ifdef CONFIG_SCHED_MC
+	{ cpu_coregroup_mask, x86_core_flags, SD_INIT_NAME(MC) },
+#endif
+	{ cpu_cpu_mask, SD_INIT_NAME(DIE) },
+	{ NULL, },
+};
+
 static struct sched_domain_topology_level x86_topology[] = {
 #ifdef CONFIG_SCHED_SMT
 	{ cpu_smt_mask, x86_smt_flags, SD_INIT_NAME(SMT) },
@@ -1469,8 +1480,11 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
 
 	calculate_max_logical_packages();
 
+	/* XXX for now assume numa-in-package and hybrid don't overlap */
 	if (x86_has_numa_in_package)
 		set_sched_topology(x86_numa_in_package_topology);
+	if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))
+		set_sched_topology(x86_hybrid_topology);
 
 	nmi_selftest();
 	impress_friends();