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Date: Thu, 10 Mar 2022 19:25:33 -0800
From: Qing Wang <wangqing@...o.com>
To: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Sudeep Holla <sudeep.holla@....com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: Wang Qing <wangqing@...o.com>
Subject: [PATCH V2] sched: topology: make cache topology separate from cpu topology
From: Wang Qing <wangqing@...o.com>
Some architectures(e.g. ARM64), caches are implemented like below:
SD(Level 1): ************ DIE ************
SD(Level 0): **** MC **** **** MC *****
cluster: **cluster 0** **cluster 1**
cores: 0 1 2 3 4 5 6 7
cache(Level 1): C C C C C C C C
cache(Level 2): **C** **C** **C** **C**
cache(Level 3): *******shared Level 3********
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 in sd, which will affect the CPU load balance.
The cost of migration in core[0-1] is different to core[2-3] within sd,
because core[0-1] shared L2 cache, but not shared with core[2-3].
Cache topology should be separated with CPU topology, it can be obtained
from "next-level-cache" in DTS preferentially.
V2:
move fix_cpu_llc() to arch_topology.c
Signed-off-by: Wang Qing <wangqing@...o.com>
---
arch/arm64/kernel/smp.c | 1 +
drivers/base/arch_topology.c | 56 +++++++++++++++++++++++++++++++++++++++++++
include/linux/arch_topology.h | 2 ++
kernel/sched/topology.c | 3 +++
4 files changed, 62 insertions(+)
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..d6e59b8
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -609,6 +609,62 @@ static int __init parse_dt_topology(void)
#endif
/*
+ * cpu cache topology table
+ */
+#define MAX_CACHE_LEVEL 7
+struct device_node *cache_topology[NR_CPUS][MAX_CACHE_LEVEL];
+
+void 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_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);
+ }
+}
+
+void fix_cpu_llc(int cpu, int *first_cpu, int *cpu_num)
+{
+ int cache_level, cpu_id;
+ int first, last;
+ int id = *first_cpu;
+ int size = *cpu_num;
+
+ for (cache_level = 0; cache_level < MAX_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)
+ return;
+
+ first = (first == -1)?cpu_id:first;
+ last = cpu_id;
+ }
+ }
+ *first_cpu = first;
+ *cpu_num = last - first + 1;
+ }
+}
+
+/*
* cpu topology table
*/
struct cpu_topology cpu_topology[NR_CPUS];
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index cce6136b..3048fa6
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -82,6 +82,8 @@ 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 fix_cpu_llc(int cpu, int *first_cpu, int *cpu_num);
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..d894ced
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -661,6 +661,9 @@ static void update_top_cache_domain(int cpu)
if (sd) {
id = cpumask_first(sched_domain_span(sd));
size = cpumask_weight(sched_domain_span(sd));
+#ifdef CONFIG_GENERIC_ARCH_TOPOLOGY
+ fix_cpu_llc(cpu, &id, &size);
+#endif
sds = sd->shared;
}
--
2.7.4
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