@@ -977,6 +977,13 @@ config SCHED_MC
making when dealing with multi-core CPU chips at a cost of slightly
increased overhead in some places. If unsure say N here.
+config SCHED_CLUSTER
+ bool "Cluster scheduler support"
+ help
+ Cluster scheduler support improves the CPU scheduler's decision
+ making when dealing with machines that have clusters(sharing internal
+ bus or sharing LLC cache tag). If unsure say N here.
+
config SCHED_SMT
bool "SMT scheduler support"
help
new file mode 100644
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_SCHED_CLUSTER_H
+#define _LINUX_SCHED_CLUSTER_H
+
+#include <linux/static_key.h>
+
+#ifdef CONFIG_SCHED_CLUSTER
+extern struct static_key_false sched_cluster_present;
+
+static __always_inline bool sched_cluster_active(void)
+{
+ return static_branch_likely(&sched_cluster_present);
+}
+#else
+static inline bool sched_cluster_active(void) { return false; }
+
+#endif
+
+#endif
@@ -42,6 +42,13 @@ static inline int cpu_smt_flags(void)
}
#endif
+#ifdef CONFIG_SCHED_CLUSTER
+static inline int cpu_cluster_flags(void)
+{
+ return SD_SHARE_PKG_RESOURCES;
+}
+#endif
+
#ifdef CONFIG_SCHED_MC
static inline int cpu_core_flags(void)
{
@@ -212,6 +212,13 @@ static inline const struct cpumask *cpu_smt_mask(int cpu)
}
#endif
+#if defined(CONFIG_SCHED_CLUSTER) && !defined(cpu_cluster_mask)
+static inline const struct cpumask *cpu_cluster_mask(int cpu)
+{
+ return topology_cluster_cpumask(cpu);
+}
+#endif
+
static inline const struct cpumask *cpu_cpu_mask(int cpu)
{
return cpumask_of_node(cpu_to_node(cpu));
@@ -7840,6 +7840,17 @@ int sched_cpu_activate(unsigned int cpu)
if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
static_branch_inc_cpuslocked(&sched_smt_present);
#endif
+
+#ifdef CONFIG_SCHED_CLUSTER
+ /*
+ * When going up, increment the number of cluster cpus with
+ * cluster present.
+ */
+ if (cpumask_weight(cpu_cluster_mask(cpu)) > cpumask_weight(cpu_smt_mask(cpu)) &&
+ cpumask_weight(cpu_cluster_mask(cpu)) < cpumask_weight(cpu_coregroup_mask(cpu)))
+ static_branch_inc_cpuslocked(&sched_cluster_present);
+#endif
+
set_cpu_active(cpu, true);
if (sched_smp_initialized) {
@@ -7916,6 +7927,15 @@ int sched_cpu_deactivate(unsigned int cpu)
static_branch_dec_cpuslocked(&sched_smt_present);
#endif
+#ifdef CONFIG_SCHED_CLUSTER
+ /*
+ * When going down, decrement the number of cpus with cluster present.
+ */
+ if (cpumask_weight(cpu_cluster_mask(cpu)) > cpumask_weight(cpu_smt_mask(cpu)) &&
+ cpumask_weight(cpu_cluster_mask(cpu)) < cpumask_weight(cpu_coregroup_mask(cpu)))
+ static_branch_dec_cpuslocked(&sched_cluster_present);
+#endif
+
if (!sched_smp_initialized)
return 0;
@@ -6021,6 +6021,10 @@ static inline int __select_idle_cpu(int cpu)
return -1;
}
+#ifdef CONFIG_SCHED_CLUSTER
+DEFINE_STATIC_KEY_FALSE(sched_cluster_present);
+#endif
+
#ifdef CONFIG_SCHED_SMT
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
EXPORT_SYMBOL_GPL(sched_smt_present);
@@ -6,6 +6,7 @@
#include <linux/sched/autogroup.h>
#include <linux/sched/clock.h>
+#include <linux/sched/cluster.h>
#include <linux/sched/coredump.h>
#include <linux/sched/cpufreq.h>
#include <linux/sched/cputime.h>
@@ -1511,6 +1511,11 @@ static void claim_allocations(int cpu, struct sched_domain *sd)
#ifdef CONFIG_SCHED_SMT
{ cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
#endif
+
+#ifdef CONFIG_SCHED_CLUSTER
+ { cpu_clustergroup_mask, cpu_cluster_flags, SD_INIT_NAME(CLS) },
+#endif
+
#ifdef CONFIG_SCHED_MC
{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
#endif
ARM64 chip Kunpeng 920 has 6 or 8 clusters in each NUMA node, and each cluster has 4 cpus. All clusters share L3 cache data, but each cluster has local L3 tag. On the other hand, each clusters will share some internal system bus. This means cache coherence overhead inside one cluster is much less than the overhead across clusters. This patch adds the sched_domain for clusters. On kunpeng 920, without this patch, domain0 of cpu0 would be MC with cpu0~cpu23 with ; with this patch, MC becomes domain1, a new domain0 "CLS" including cpu0-cpu3. This will help spread unrelated tasks among clusters, thus decrease the contention and improve the throughput, for example, stream benchmark can improve 20%+ while parallelism is 6 and improve around 5% while paralle- lism is 12: (1) -P <parallelism> 6 $ numactl -N 0 /usr/lib/lmbench/bin/stream -P 6 -M 1024M -N 5 w/o patch: STREAM copy latency: 2.46 nanoseconds STREAM copy bandwidth: 39096.28 MB/sec STREAM scale latency: 2.46 nanoseconds STREAM scale bandwidth: 38970.26 MB/sec STREAM add latency: 4.45 nanoseconds STREAM add bandwidth: 32332.04 MB/sec STREAM triad latency: 4.07 nanoseconds STREAM triad bandwidth: 35387.69 MB/sec w/ patch: STREAM copy latency: 2.02 nanoseconds STREAM copy bandwidth: 47604.47 MB/sec +21.7% STREAM scale latency: 2.04 nanoseconds STREAM scale bandwidth: 47066.84 MB/sec +20.8% STREAM add latency: 3.35 nanoseconds STREAM add bandwidth: 42942.15 MB/sec +32.8% STREAM triad latency: 3.16 nanoseconds STREAM triad bandwidth: 45619.18 MB/sec +28.9% On the other hand,stream result could change significantly during different tests without the patch, eg: a. STREAM copy latency: 2.16 nanoseconds STREAM copy bandwidth: 44448.45 MB/sec STREAM scale latency: 2.17 nanoseconds STREAM scale bandwidth: 44320.77 MB/sec STREAM add latency: 3.77 nanoseconds STREAM add bandwidth: 38230.54 MB/sec STREAM triad latency: 3.88 nanoseconds STREAM triad bandwidth: 37072.10 MB/sec b. STREAM copy latency: 2.16 nanoseconds STREAM copy bandwidth: 44403.22 MB/sec STREAM scale latency: 2.39 nanoseconds STREAM scale bandwidth: 40173.69 MB/sec STREAM add latency: 3.77 nanoseconds STREAM add bandwidth: 38232.56 MB/sec STREAM triad latency: 3.38 nanoseconds STREAM triad bandwidth: 42592.04 MB/sec Obviously it is because the 6 threads are put randomly in 6 cores. Sometimes they are packed in clusters, sometimes they are spread widely. (2) -P <parallelism> 12 $ numactl -N 0 /usr/lib/lmbench/bin/stream -P 12 -M 1024M -N 5 w/o patch: STREAM copy latency: 3.37 nanoseconds STREAM copy bandwidth: 57008.80 MB/sec STREAM scale latency: 3.38 nanoseconds STREAM scale bandwidth: 56848.47 MB/sec STREAM add latency: 5.50 nanoseconds STREAM add bandwidth: 52398.62 MB/sec STREAM triad latency: 5.09 nanoseconds STREAM triad bandwidth: 56591.60 MB/sec w/ patch: STREAM copy latency: 3.24 nanoseconds STREAM copy bandwidth: 59338.60 MB/sec +4.1% STREAM scale latency: 3.25 nanoseconds STREAM scale bandwidth: 58993.23 MB/sec +3.7% STREAM add latency: 5.19 nanoseconds STREAM add bandwidth: 55517.45 MB/sec +5.9% STREAM triad latency: 4.86 nanoseconds STREAM triad bandwidth: 59245.34 MB/sec +4.7% To evaluate the performance impact to related tasks talking with each other, we run the below hackbench with different -g parameter from 2 to 14, for each different g, we run the command 10 times and get the average time: $ numactl -N 0 hackbench -p -T -l 20000 -g $1 hackbench will report the time which is needed to complete a certain number of messages transmissions between a certain number of tasks, for example: $ numactl -N 0 hackbench -p -T -l 20000 -g 10 Running in threaded mode with 10 groups using 40 file descriptors each (== 400 tasks) Each sender will pass 20000 messages of 100 bytes The below is the result of hackbench w/ and w/o the patch: g= 2 4 6 8 10 12 14 w/o: 1.8151 3.8499 5.5142 7.2491 9.0340 10.7345 12.0929 w/ : 1.8396 3.8250 5.4780 7.3442 9.0172 10.5950 11.9113 Obviously this patch doesn't impact hackbench too much. Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> --- arch/arm64/Kconfig | 7 +++++++ include/linux/sched/cluster.h | 19 +++++++++++++++++++ include/linux/sched/topology.h | 7 +++++++ include/linux/topology.h | 7 +++++++ kernel/sched/core.c | 20 ++++++++++++++++++++ kernel/sched/fair.c | 4 ++++ kernel/sched/sched.h | 1 + kernel/sched/topology.c | 5 +++++ 8 files changed, 70 insertions(+) create mode 100644 include/linux/sched/cluster.h