Messages in this thread Patch in this message | | | From | Ricardo Neri <> | Subject | [PATCH v2 6/7] x86/sched/itmt: Give all SMT siblings of a core the same priority | Date | Tue, 22 Nov 2022 12:35:31 -0800 |
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Currently, each SMT sibling is given a priority that ensures that in partially busy systems load is evenly spread among cores.
There is, however, no difference in performance among the SMT siblings of a core.
Having different priorities for each SMT sibling triggers unnecessary load balancing towards the higher-priority sibling.
Cc: Ben Segall <bsegall@google.com> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Len Brown <len.brown@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tim C. Chen <tim.c.chen@intel.com> Cc: Valentin Schneider <vschneid@redhat.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Len Brown <len.brown@intel.com> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> --- Changes since v1: * Reworded commit message for clarity. --- arch/x86/kernel/itmt.c | 23 +++++------------------ 1 file changed, 5 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kernel/itmt.c b/arch/x86/kernel/itmt.c index 4cb5a5e4fa47..2be49ce4f94a 100644 --- a/arch/x86/kernel/itmt.c +++ b/arch/x86/kernel/itmt.c @@ -174,32 +174,19 @@ int arch_asym_cpu_priority(int cpu, bool check_smt) /** * sched_set_itmt_core_prio() - Set CPU priority based on ITMT - * @prio: Priority of cpu core - * @core_cpu: The cpu number associated with the core + * @prio: Priority of @cpu + * @cpu: The CPU number * * The pstate driver will find out the max boost frequency * and call this function to set a priority proportional - * to the max boost frequency. CPU with higher boost + * to the max boost frequency. CPUs with higher boost * frequency will receive higher priority. * * No need to rebuild sched domain after updating * the CPU priorities. The sched domains have no * dependency on CPU priorities. */ -void sched_set_itmt_core_prio(int prio, int core_cpu) +void sched_set_itmt_core_prio(int prio, int cpu) { - int cpu, i = 1; - - for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) { - int smt_prio; - - /* - * Ensure that the siblings are moved to the end - * of the priority chain and only used when - * all other high priority cpus are out of capacity. - */ - smt_prio = prio * smp_num_siblings / (i * i); - per_cpu(sched_core_priority, cpu) = smt_prio; - i++; - } + per_cpu(sched_core_priority, cpu) = prio; } -- 2.25.1
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