[PATCH 2/3] scheduler: Add cluster scheduler level in core and related Kconfig for ARM64

Barry Song
2021-08-20T01:31:22Z

From: Barry Song <song.bao.hua@hisilicon.com>

This patch adds scheduler level for clusters and automatically enables
the load balance among clusters. It will directly benefit a lot of
workload which loves more resources such as memory bandwidth, caches.

Testing has widely been done in two different hardware configurations of
Kunpeng920:

24 cores in one NUMA(6 clusters in each NUMA node);
32 cores in one NUMA(8 clusters in each NUMA node)

Workload is running on either one NUMA node or four NUMA nodes, thus,
this can estimate the effect of cluster spreading w/ and w/o NUMA load
balance.

* Stream benchmark:

4threads stream (on 1NUMA * 24cores = 24cores)
stream stream
w/o patch w/ patch
MB/sec copy 29929.64 ( 0.00%) 32932.68 ( 10.03%)
MB/sec scale 29861.10 ( 0.00%) 32710.58 ( 9.54%)
MB/sec add 27034.42 ( 0.00%) 32400.68 ( 19.85%)
MB/sec triad 27225.26 ( 0.00%) 31965.36 ( 17.41%)

6threads stream (on 1NUMA * 24cores = 24cores)
stream stream
w/o patch w/ patch
MB/sec copy 40330.24 ( 0.00%) 42377.68 ( 5.08%)
MB/sec scale 40196.42 ( 0.00%) 42197.90 ( 4.98%)
MB/sec add 37427.00 ( 0.00%) 41960.78 ( 12.11%)
MB/sec triad 37841.36 ( 0.00%) 42513.64 ( 12.35%)

12threads stream (on 1NUMA * 24cores = 24cores)
stream stream
w/o patch w/ patch
MB/sec copy 52639.82 ( 0.00%) 53818.04 ( 2.24%)
MB/sec scale 52350.30 ( 0.00%) 53253.38 ( 1.73%)
MB/sec add 53607.68 ( 0.00%) 55198.82 ( 2.97%)
MB/sec triad 54776.66 ( 0.00%) 56360.40 ( 2.89%)

Thus, it could help memory-bound workload especially under medium load.
Similar improvement is also seen in lkp-pbzip2:

* lkp-pbzip2 benchmark

2-96 threads (on 4NUMA * 24cores = 96cores)
lkp-pbzip2 lkp-pbzip2
w/o patch w/ patch
Hmean tput-2 11062841.57 ( 0.00%) 11341817.51 * 2.52%*
Hmean tput-5 26815503.70 ( 0.00%) 27412872.65 * 2.23%*
Hmean tput-8 41873782.21 ( 0.00%) 43326212.92 * 3.47%*
Hmean tput-12 61875980.48 ( 0.00%) 64578337.51 * 4.37%*
Hmean tput-21 105814963.07 ( 0.00%) 111381851.01 * 5.26%*
Hmean tput-30 150349470.98 ( 0.00%) 156507070.73 * 4.10%*
Hmean tput-48 237195937.69 ( 0.00%) 242353597.17 * 2.17%*
Hmean tput-79 360252509.37 ( 0.00%) 362635169.23 * 0.66%*
Hmean tput-96 394571737.90 ( 0.00%) 400952978.48 * 1.62%*

2-24 threads (on 1NUMA * 24cores = 24cores)
lkp-pbzip2 lkp-pbzip2
w/o patch w/ patch
Hmean tput-2 11071705.49 ( 0.00%) 11296869.10 * 2.03%*
Hmean tput-4 20782165.19 ( 0.00%) 21949232.15 * 5.62%*
Hmean tput-6 30489565.14 ( 0.00%) 33023026.96 * 8.31%*
Hmean tput-8 40376495.80 ( 0.00%) 42779286.27 * 5.95%*
Hmean tput-12 61264033.85 ( 0.00%) 62995632.78 * 2.83%*
Hmean tput-18 86697139.39 ( 0.00%) 86461545.74 ( -0.27%)
Hmean tput-24 104854637.04 ( 0.00%) 104522649.46 * -0.32%*

In the case of 6 threads and 8 threads, we see the greatest performance
improvement.

Similar improvement can be seen on lkp-pixz though the improvement is
smaller:

* lkp-pixz benchmark

2-24 threads lkp-pixz (on 1NUMA * 24cores = 24cores)
lkp-pixz lkp-pixz
w/o patch w/ patch
Hmean tput-2 6486981.16 ( 0.00%) 6561515.98 * 1.15%*
Hmean tput-4 11645766.38 ( 0.00%) 11614628.43 ( -0.27%)
Hmean tput-6 15429943.96 ( 0.00%) 15957350.76 * 3.42%*
Hmean tput-8 19974087.63 ( 0.00%) 20413746.98 * 2.20%*
Hmean tput-12 28172068.18 ( 0.00%) 28751997.06 * 2.06%*
Hmean tput-18 39413409.54 ( 0.00%) 39896830.55 * 1.23%*
Hmean tput-24 49101815.85 ( 0.00%) 49418141.47 * 0.64%*

* SPECrate benchmark

4,8,16 copies mcf_r(on 1NUMA * 32cores = 32cores)
Base Base
Run Time Rate
------- ---------
4 Copies w/o 580 (w/ 570) w/o 11.1 (w/ 11.3)
8 Copies w/o 647 (w/ 605) w/o 20.0 (w/ 21.4, +7%)
16 Copies w/o 844 (w/ 844) w/o 30.6 (w/ 30.6)

32 Copies(on 4NUMA * 32 cores = 128cores)
[w/o patch]
Base Base Base
Benchmarks Copies Run Time Rate
--------------- ------- --------- ---------
500.perlbench_r 32 584 87.2 *
502.gcc_r 32 503 90.2 *
505.mcf_r 32 745 69.4 *
520.omnetpp_r 32 1031 40.7 *
523.xalancbmk_r 32 597 56.6 *
525.x264_r 1 -- CE
531.deepsjeng_r 32 336 109 *
541.leela_r 32 556 95.4 *
548.exchange2_r 32 513 163 *
557.xz_r 32 530 65.2 *
Est. SPECrate2017_int_base 80.3

[w/ patch]
Base Base Base
Benchmarks Copies Run Time Rate
--------------- ------- --------- ---------
500.perlbench_r 32 580 87.8 (+0.688%) *
502.gcc_r 32 477 95.1 (+5.432%) *
505.mcf_r 32 644 80.3 (+13.574%) *
520.omnetpp_r 32 942 44.6 (+9.58%) *
523.xalancbmk_r 32 560 60.4 (+6.714%%) *
525.x264_r 1 -- CE
531.deepsjeng_r 32 337 109 (+0.000%) *
541.leela_r 32 554 95.6 (+0.210%) *
548.exchange2_r 32 515 163 (+0.000%) *
557.xz_r 32 524 66.0 (+1.227%) *
Est. SPECrate2017_int_base 83.7 (+4.062%)

On the other hand, it is slightly helpful to CPU-bound tasks like
kernbench:

* 24-96 threads kernbench (on 4NUMA * 24cores = 96cores)
kernbench kernbench
w/o cluster w/ cluster
Min user-24 12054.67 ( 0.00%) 12024.19 ( 0.25%)
Min syst-24 1751.51 ( 0.00%) 1731.68 ( 1.13%)
Min elsp-24 600.46 ( 0.00%) 598.64 ( 0.30%)
Min user-48 12361.93 ( 0.00%) 12315.32 ( 0.38%)
Min syst-48 1917.66 ( 0.00%) 1892.73 ( 1.30%)
Min elsp-48 333.96 ( 0.00%) 332.57 ( 0.42%)
Min user-96 12922.40 ( 0.00%) 12921.17 ( 0.01%)
Min syst-96 2143.94 ( 0.00%) 2110.39 ( 1.56%)
Min elsp-96 211.22 ( 0.00%) 210.47 ( 0.36%)
Amean user-24 12063.99 ( 0.00%) 12030.78 * 0.28%*
Amean syst-24 1755.20 ( 0.00%) 1735.53 * 1.12%*
Amean elsp-24 601.60 ( 0.00%) 600.19 ( 0.23%)
Amean user-48 12362.62 ( 0.00%) 12315.56 * 0.38%*
Amean syst-48 1921.59 ( 0.00%) 1894.95 * 1.39%*
Amean elsp-48 334.10 ( 0.00%) 332.82 * 0.38%*
Amean user-96 12925.27 ( 0.00%) 12922.63 ( 0.02%)
Amean syst-96 2146.66 ( 0.00%) 2122.20 * 1.14%*
Amean elsp-96 211.96 ( 0.00%) 211.79 ( 0.08%)

Note this patch isn't an universal win, it might hurt those workload
which can benefit from packing. Though tasks which want to take
advantages of lower communication latency of one cluster won't
necessarily been packed in one cluster while kernel is not aware of
clusters, they have some chance to been randomly packed. But this
patch will make them spread anyway.

Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
---
arch/arm64/Kconfig | 7 +++++++
include/linux/sched/topology.h | 7 +++++++
include/linux/topology.h | 7 +++++++
kernel/sched/topology.c | 5 +++++
4 files changed, 26 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fdcd54d39c1e..7a3cc2314a03 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -992,6 +992,13 @@ 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
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 8f0f778b7c91..2f9166f6dec8 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -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)
{
diff --git a/include/linux/topology.h b/include/linux/topology.h
index 80d27d717631..0b3704ad13c8 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -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));
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index b77ad49dc14f..546cfb1c728e 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1625,6 +1625,11 @@ static struct sched_domain_topology_level default_topology[] = {
#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
--
2.25.1