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authorJorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>2015-05-25 19:46:50 -0400
committerKevin Hilman <khilman@linaro.org>2015-05-26 09:28:55 -0700
commit646fe96c67a5fcc2cfffb7326b2299f2714f7f27 (patch)
tree238261a9ef88cd4849235db8e08dd2ab32f6c3c5
parentee22524dbe4fcbaa8186296d197e73982a935565 (diff)
downloadlinux-linaro-stable-v3.10/topic/arm64-hmp.tar.gz
arm64: topology: fix cpu power calculationv3.10/topic/arm64-hmp
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. 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 incorrect scheduling decisions typically overallocating all the work on one of the CPU cores. This proposed solution to arm64 is in line with the upstream solution present in arm32 since the commit below was merged: * SHA: 816a8de0017f16c32e747abc5367bf379515b20a * From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com> * Date: Mon, 17 Jun 2013 14:20:00 +0100 * Subject: ARM: topology: remove hwid/MPIDR dependency from cpu_capac Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Kevin Hilman <khilman@linaro.org>
-rw-r--r--arch/arm64/kernel/topology.c8
1 files changed, 2 insertions, 6 deletions
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 49c94ff..b966bc3 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -315,16 +315,12 @@ 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