sched: Add a new function to compare if two cpus have the same capacity

The new helper function is needed to help blk-mq check if it needs to
dispatch the softirq on another CPU to match the performance level the
IO requester is running at. This is important on HMP systems where not
all CPUs have the same compute capacity.

Signed-off-by: Qais Yousef <qyousef@layalina.io>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240223155749.2958009-2-qyousef@layalina.io
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index a6e04b4a21d70f9d3c807970815d1b79fee74ed4..11e0e00e0bb95599a0efebdefe6ebb9a5288b0c4 100644 (file)
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -176,6 +176,7 @@ extern void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
 cpumask_var_t *alloc_sched_domains(unsigned int ndoms);
 void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms);
 
+bool cpus_equal_capacity(int this_cpu, int that_cpu);
 bool cpus_share_cache(int this_cpu, int that_cpu);
 bool cpus_share_resources(int this_cpu, int that_cpu);
 
@@ -226,6 +227,11 @@ partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
 {
 }
 
+static inline bool cpus_equal_capacity(int this_cpu, int that_cpu)
+{
+       return true;
+}
+
 static inline bool cpus_share_cache(int this_cpu, int that_cpu)
 {
        return true;

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 083f2258182d899c44d5436ad8ff7097c24b3ebd..540f229700b62c3e2d3f084ce68549251ad39be8 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3955,6 +3955,17 @@ void wake_up_if_idle(int cpu)
        }
 }
 
+bool cpus_equal_capacity(int this_cpu, int that_cpu)
+{
+       if (!sched_asym_cpucap_active())
+               return true;
+
+       if (this_cpu == that_cpu)
+               return true;
+
+       return arch_scale_cpu_capacity(this_cpu) == arch_scale_cpu_capacity(that_cpu);
+}
+
 bool cpus_share_cache(int this_cpu, int that_cpu)
 {
        if (this_cpu == that_cpu)