timers/migration: Temporarily disable per capacity hierarchies

Some workloads with different CPU capacities consume more power with
timer migration than before. The recently introduced per capacity
hierarchies were supposed to alleviate this problem. However it appears
to also regress other types of workloads, especially when plenty of
capacities live together in the same machine.

Disable the feature until a reasonable solution is found.

Fixes: 098cbaad8e57 ("timers/migration: Split per-capacity hierarchies")
Reported-by: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260609123356.28449-1-frederic@kernel.org
Closes: https://lore.kernel.org/all/3b79338f-6cfc-4722-8062-9103db2c8ad1@arm.com

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index 548d84955f4cef52cedcb020bca18b094789f587..e9d96d96e251a5cb2651bd09aa5a86387dd08ffe 100644 (file)
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1473,7 +1473,7 @@ static unsigned int tmigr_get_capacity(int cpu)
         * timekeeper must then belong to the same hierarchy as all the nohz_full
         * CPUs. Simply turn off capacity awareness when nohz_full is running.
         */
-       if (tick_nohz_full_enabled())
+       if (tick_nohz_full_enabled() || !IS_ENABLED(CONFIG_BROKEN))
                return SCHED_CAPACITY_SCALE;
        else
                return arch_scale_cpu_capacity(cpu);