[v1,2/2] PM: EM: Slightly reduce em_check_capacity_update() overhead

Commit Message

Rafael J. Wysocki Jan. 27, 2025, 1:38 p.m. UTC

From: Rafael J. Wysocki <[e-mail]>

Every iteration of the loop over all possible CPUs in
em_check_capacity_update() causes get_cpu_device() to be called twice
for the same CPU, once indirectly via em_cpu_get() and once directly.

Get rid of the indirect get_cpu_device() call by moving the direct
invocation of it earlier and using em_pd_get() instead of em_cpu_get()
to get a pd pointer for the dev one returned by it.

This also exposes the fact that dev is needed to get a pd, so the code
becomes somewhat easier to follow after it.

No functional impact.

Signed-off-by: Rafael J. Wysocki <[e-mail]>
---
 kernel/power/energy_model.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -774,7 +774,8 @@ 
 		}
 		cpufreq_cpu_put(policy);
 
-		pd = em_cpu_get(cpu);
+		dev = get_cpu_device(cpu);
+		pd = em_pd_get(dev);
 		if (!pd || em_is_artificial(pd))
 			continue;
 
@@ -798,7 +799,6 @@ 
 		pr_debug("updating cpu%d cpu_cap=%lu old capacity=%lu\n",
 			 cpu, cpu_capacity, em_max_perf);
 
-		dev = get_cpu_device(cpu);
 		em_adjust_new_capacity(dev, pd);
 	}