This commit sets the power of the average CPU in SMP systems to SCHED_CAPACITY_SCALE.

Ignoring the condition "min_capacity==max_capacity" causes the function update_cpu_power( .. ) to generate out of range values [1]. This is because the default value of middle_capacity is used in the final calculation instead of a valid scaling factor.

Incidentally, when out of range values are generated and if SCHED_FEAT(ARCH_POWER) is true) the load balancing algorithm makes the wrong decisions typically overallocating work on one of the cores while leaving the others unused.

Signed-off-by: Jorge Ramirez-Ortiz jorge.ramirez-ortiz@linaro.org --- arch/arm64/kernel/topology.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index db8bb29..31e3e6e 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -317,16 +317,12 @@ static void __init parse_dt_cpu_power(void) cpu_capacity(cpu) = capacity; }

- /* If min and max capacities are equal we bypass the update of the - * cpu_scale because all CPUs have the same capacity. Otherwise, we - * compute a middle_capacity factor that will ensure that the capacity + /* compute a middle_capacity factor that will ensure that the capacity * of an 'average' CPU of the system will be as close as possible to * SCHED_POWER_SCALE, which is the default value, but with the * constraint explained near table_efficiency[]. */ - if (min_capacity == max_capacity) - return; - else if (4 * max_capacity < (3 * (max_capacity + min_capacity))) + if (4 * max_capacity < (3 * (max_capacity + min_capacity))) middle_capacity = (min_capacity + max_capacity) >> (SCHED_POWER_SHIFT+1); else