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A single fix for the x86 scheduler topology:

Browse Source 
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.
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Merge tag 'sched-urgent-2021-12-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fix from Thomas Gleixner:
 "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"

* tag 'sched-urgent-2021-12-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched,x86: Don't use cluster topology for x86 hybrid CPUs
This commit is contained in:
Linus Torvalds 2021-12-12 09:38:04 -08:00
commit 773602256a
1 changed files with 14 additions and 0 deletions
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14
arch/x86/kernel/smpboot.c
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@ -579,6 +579,17 @@ static struct sched_domain_topology_level x86_numa_in_package_topology[] = {
{ NULL, }, { 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[] = { static struct sched_domain_topology_level x86_topology[] = {
#ifdef CONFIG_SCHED_SMT #ifdef CONFIG_SCHED_SMT
{ cpu_smt_mask, x86_smt_flags, SD_INIT_NAME(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(); calculate_max_logical_packages();
/* XXX for now assume numa-in-package and hybrid don't overlap */
if (x86_has_numa_in_package) if (x86_has_numa_in_package)
set_sched_topology(x86_numa_in_package_topology); set_sched_topology(x86_numa_in_package_topology);
if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))
set_sched_topology(x86_hybrid_topology);
nmi_selftest(); nmi_selftest();
impress_friends(); impress_friends();