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Subject[PATCH] sched: topology: make cache topology separate from cpu topology
Date
From: Wang Qing <wangqing@vivo.com>

Some architectures(e.g. ARM64), caches are implemented below:
cluster: ****** cluster 0 ***** ****** cluster 1 *****
core: 0 1 2 3 4 5 6 7
cache(Leveln): **cache0** **cache1** **cache2** **cache3**
sd_llc_id(current): 0 0 0 0 4 4 4 4
sd_llc_id(should be): 0 0 2 2 4 4 6 6

Caches and cpus have different topology, this causes cpus_share_cache()
return the wrong value, which will affect the CPU load balance.

Cache topology should be separated with CPU topology, it can be obtained
from "next-level-cache" in DTS preferentially.

Signed-off-by: Wang Qing <wangqing@vivo.com>
---
arch/arm64/kernel/smp.c | 1 +
drivers/base/arch_topology.c | 23 +++++++++++++++++++++++
include/linux/arch_topology.h | 3 +++
kernel/sched/topology.c | 33 +++++++++++++++++++++++++++++++--
4 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 27df5c1..94cf649
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -723,6 +723,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
unsigned int this_cpu;

init_cpu_topology();
+ init_cpu_cache_topology();

this_cpu = smp_processor_id();
store_cpu_topology(this_cpu);
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 9761541..613213f
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -613,6 +613,7 @@ static int __init parse_dt_topology(void)
*/
struct cpu_topology cpu_topology[NR_CPUS];
EXPORT_SYMBOL_GPL(cpu_topology);
+struct device_node *cache_topology[NR_CPUS][MAX_CPU_CACHE_LEVEL];

const struct cpumask *cpu_coregroup_mask(int cpu)
{
@@ -738,4 +739,26 @@ void __init init_cpu_topology(void)
else if (of_have_populated_dt() && parse_dt_topology())
reset_cpu_topology();
}
+
+void __init init_cpu_cache_topology(void)
+{
+ struct device_node *node_cpu, *node_cache;
+ int cpu, level;
+
+ for_each_possible_cpu(cpu) {
+ node_cpu = of_get_cpu_node(cpu, NULL);
+ if (!node_cpu)
+ continue;
+
+ level = 0;
+ node_cache = node_cpu;
+ while (level < MAX_CPU_CACHE_LEVEL) {
+ node_cache = of_parse_phandle(node_cache, "next-level-cache", 0);
+ if (!node_cache)
+ break;
+ cache_topology[cpu][level++] = node_cache;
+ }
+ of_node_put(node_cpu);
+ }
+}
#endif
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index cce6136b..d37f47d
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -72,6 +72,8 @@ struct cpu_topology {
};

#ifdef CONFIG_GENERIC_ARCH_TOPOLOGY
+#define MAX_CPU_CACHE_LEVEL 7
+extern struct device_node *cache_topology[NR_CPUS][MAX_CPU_CACHE_LEVEL];
extern struct cpu_topology cpu_topology[NR_CPUS];

#define topology_physical_package_id(cpu) (cpu_topology[cpu].package_id)
@@ -82,6 +84,7 @@ extern struct cpu_topology cpu_topology[NR_CPUS];
#define topology_cluster_cpumask(cpu) (&cpu_topology[cpu].cluster_sibling)
#define topology_llc_cpumask(cpu) (&cpu_topology[cpu].llc_sibling)
void init_cpu_topology(void);
+void init_cpu_cache_topology(void);
void store_cpu_topology(unsigned int cpuid);
const struct cpumask *cpu_coregroup_mask(int cpu);
const struct cpumask *cpu_clustergroup_mask(int cpu);
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index d201a70..10850d6
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -650,6 +650,36 @@ DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);

+static void set_sd_llc(int cpu, struct sched_domain *sd, int *first_cpu, int *cpu_num)
+{
+ int cache_level, cpu_id;
+ int first, last;
+ int id = cpumask_first(sched_domain_span(sd));
+ int size = cpumask_weight(sched_domain_span(sd));
+
+ *first_cpu = id;
+ *cpu_num = size;
+
+ for (cache_level = 0; cache_level < MAX_CPU_CACHE_LEVEL; cache_level++) {
+ if (!cache_topology[cpu][cache_level])
+ break;
+
+ first = -1;
+ last = id;
+ for (cpu_id = 0; cpu_id < NR_CPUS; cpu_id++) {
+ if (cache_topology[cpu][cache_level] == cache_topology[cpu_id][cache_level]) {
+ if (cpu_id >= id && cpu_id < id + size) {
+ first = (first == -1)?cpu_id:first;
+ last = cpu_id;
+ } else
+ return;
+ }
+ }
+ *first_cpu = first;
+ *cpu_num = last - first + 1;
+ }
+}
+
static void update_top_cache_domain(int cpu)
{
struct sched_domain_shared *sds = NULL;
@@ -659,8 +689,7 @@ static void update_top_cache_domain(int cpu)

sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
if (sd) {
- id = cpumask_first(sched_domain_span(sd));
- size = cpumask_weight(sched_domain_span(sd));
+ set_sd_llc(cpu, sd, &id, &size);
sds = sd->shared;
}

--
2.7.4
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