From c64380cab52e16999118514e6528234ef107a2c9 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Sat, 4 Dec 2021 10:14:02 +0100 Subject: [PATCH] sched,x86: Don't use cluster topology for x86 hybrid CPUs For x86 hybrid CPUs like Alder Lake, the order of CPU selection should be based strictly on CPU priority. Don't include cluster topology for hybrid CPUs to avoid interference with such CPU selection order. On Alder Lake, the Atom CPU cluster has more capacity (4 Atom CPUs) vs Big core cluster (2 hyperthread CPUs). This could potentially bias CPU selection towards Atom over Big Core, when Big core CPU has higher priority. Fixes: 09c4ff723f4d ("sched: Add cluster scheduler level for x86") Suggested-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Acked-by: Tim Chen Tested-by: Ricardo Neri Link: https://lkml.kernel.org/r/20211204091402.GM16608@worktop.programming.kicks-ass.net --- 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 ac2909f0cab34..617012f4619f0 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(); -- 2.39.5