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authorJuri Lelli <juri.lelli@arm.com>2015-01-27 11:24:59 +0000
committerRobin Randhawa <robin.randhawa@arm.com>2015-04-09 12:26:15 +0100
commit5c4ee2a3d4f44328e35140a5ef82e918d258aca1 (patch)
tree06dbcc61ab22f0bd97101681d53362a6ddd5cd0e
parentce35a6abe5dcc43f7d7fdeaa037e6799e445fe6d (diff)
downloadkernel-5c4ee2a3d4f44328e35140a5ef82e918d258aca1.tar.gz
arm64: Cpu invariant scheduler load-tracking support
Counterpart of the arm bits (slightly different implementation due to different parsing of the dtb). Signed-off-by: Juri Lelli <juri.lelli@arm.com>
-rw-r--r--arch/arm64/kernel/topology.c60
1 files changed, 20 insertions, 40 deletions
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 59a48b8..1bbf173 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -197,9 +197,7 @@ struct cpu_efficiency {
* Table of relative efficiency of each processors
* The efficiency value must fit in 20bit and the final
* cpu_scale value must be in the range
- * 0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2
- * in order to return at most 1 when DIV_ROUND_CLOSEST
- * is used to compute the capacity of a CPU.
+ * 0 < cpu_scale < SCHED_CAPACITY_SCALE.
* Processors that are not defined in the table,
* use the default SCHED_CAPACITY_SCALE value for cpu_scale.
*/
@@ -212,15 +210,11 @@ static const struct cpu_efficiency table_efficiency[] = {
static unsigned long *__cpu_capacity;
#define cpu_capacity(cpu) __cpu_capacity[cpu]
-static unsigned long middle_capacity = 1;
+static unsigned long max_cpu_perf;
/*
* Iterate all CPUs' descriptor in DT and compute the efficiency
- * (as per table_efficiency). Also calculate a middle efficiency
- * as close as possible to (max{eff_i} - min{eff_i}) / 2
- * This is later used to scale the cpu_capacity field such that an
- * 'average' CPU is of middle capacity. Also see the comments near
- * table_efficiency[] and update_cpu_capacity().
+ * (as per table_efficiency). Calculate the max cpu performance too.
*/
static int __init parse_dt_topology(void)
{
@@ -269,9 +263,6 @@ static void __init parse_dt_cpu_capacity(void)
{
const struct cpu_efficiency *cpu_eff;
struct device_node *cn;
- unsigned long min_capacity = ULONG_MAX;
- unsigned long max_capacity = 0;
- unsigned long capacity = 0;
int cpu;
__cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity),
@@ -280,6 +271,7 @@ static void __init parse_dt_cpu_capacity(void)
for_each_possible_cpu(cpu) {
const u32 *rate;
int len;
+ unsigned long cpu_perf;
/* Too early to use cpu->of_node */
cn = of_get_cpu_node(cpu, NULL);
@@ -304,47 +296,35 @@ static void __init parse_dt_cpu_capacity(void)
continue;
}
- capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
-
- /* Save min capacity of the system */
- if (capacity < min_capacity)
- min_capacity = capacity;
-
- /* Save max capacity of the system */
- if (capacity > max_capacity)
- max_capacity = capacity;
-
- cpu_capacity(cpu) = capacity;
+ cpu_perf = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
+ cpu_capacity(cpu) = cpu_perf;
+ max_cpu_perf = max(max_cpu_perf, cpu_perf);
}
- /* 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
- * of an 'average' CPU of the system will be as close as possible to
- * SCHED_CAPACITY_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)))
- middle_capacity = (min_capacity + max_capacity)
- >> (SCHED_CAPACITY_SHIFT+1);
- else
- middle_capacity = ((max_capacity / 3)
- >> (SCHED_CAPACITY_SHIFT-1)) + 1;
+ if (cpu < num_possible_cpus())
+ max_cpu_perf = 0;
}
/*
* Look for a customed capacity of a CPU in the cpu_topo_data table during the
* boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
- * function returns directly for SMP system.
+ * function returns directly for SMP system or if there is no complete set
+ * of cpu efficiency, clock frequency data for each cpu.
*/
static void update_cpu_capacity(unsigned int cpu)
{
+ unsigned long capacity;
+
if (!cpu_capacity(cpu))
return;
- set_capacity_scale(cpu, cpu_capacity(cpu) / middle_capacity);
+ if (!max_cpu_perf)
+ cpu_capacity(cpu) = 0;
+
+ capacity = cpu_capacity(cpu);
+ capacity *= SCHED_CAPACITY_SCALE;
+ capacity /= max_cpu_perf;
+ set_capacity_scale(cpu, capacity);
pr_info("CPU%d: update cpu_capacity %lu\n",
cpu, arch_scale_cpu_capacity(NULL, cpu));