From: Barry Song <[email protected]>
ARM64 machines like kunpeng920 and x86 machines like Jacobsville have a
level of hardware topology in which some CPU cores, typically 4 cores,
share L3 tags or L2 cache.
That means spreading those tasks between clusters will bring more memory
bandwidth and decrease cache contention. But packing tasks might help
decrease the latency of cache synchronization.
We have three series to bring up cluster level scheduler in kernel.
This is the first series.
1st series(this one): make kernel aware of cluster, expose cluster to sysfs
ABI and add SCHED_CLUSTER which can make load balance among clusters to
benefit lots of workload.
Testing shows this can hugely boost the performance, for example, this
can increase 25.1% of SPECrate mcf on Jacobsville and 13.574% of mcf
on kunpeng920.
2nd series(packing path): modify the wake_affine and let kernel select CPUs
within cluster first before scanning the whole LLC so that we can benefit
from the lower latency of the communication within one single cluster.
this series is much more tricky. so we would like to send it after the 1st
series settles down. Prototype here:
https://op-lists.linaro.org/pipermail/linaro-open-discussions/2021-June/000219.html
3rd series: a sysctl to permit users to enable or disable cluster scheduler
from Tim Chen. Prototype here:
Add run time sysctl to enable/disable cluster scheduling
https://op-lists.linaro.org/pipermail/linaro-open-discussions/2021-July/000258.html
This series is rebased on Greg's driver-core-next with the update in topology
sysfs ABI.
-V1:
differences with RFC v6
* rebased on top of the latest update in topology sysfs ABI of Greg's
driver-core-next
* removed wake_affine path modifcation, which will be separately b2nd series
* cluster_id is gotten by detecting valid ID before falling back to use offset
* lots of benchmark data from both x86 Jacobsville and ARM64 kunpeng920
-RFC v6:
https://lore.kernel.org/lkml/[email protected]/
Barry Song (1):
scheduler: Add cluster scheduler level in core and related Kconfig for
ARM64
Jonathan Cameron (1):
topology: Represent clusters of CPUs within a die
Tim Chen (1):
scheduler: Add cluster scheduler level for x86
.../ABI/stable/sysfs-devices-system-cpu | 15 +++++
Documentation/admin-guide/cputopology.rst | 12 ++--
arch/arm64/Kconfig | 7 ++
arch/arm64/kernel/topology.c | 2 +
arch/x86/Kconfig | 8 +++
arch/x86/include/asm/smp.h | 7 ++
arch/x86/include/asm/topology.h | 3 +
arch/x86/kernel/cpu/cacheinfo.c | 1 +
arch/x86/kernel/cpu/common.c | 3 +
arch/x86/kernel/smpboot.c | 44 +++++++++++-
drivers/acpi/pptt.c | 67 +++++++++++++++++++
drivers/base/arch_topology.c | 14 ++++
drivers/base/topology.c | 10 +++
include/linux/acpi.h | 5 ++
include/linux/arch_topology.h | 5 ++
include/linux/sched/topology.h | 7 ++
include/linux/topology.h | 13 ++++
kernel/sched/topology.c | 5 ++
18 files changed, 223 insertions(+), 5 deletions(-)
--
2.25.1
From: Barry Song <[email protected]>
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 <[email protected]>
Signed-off-by: Barry Song <[email protected]>
---
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
From: Tim Chen <[email protected]>
There are x86 CPU architectures (e.g. Jacobsville) where L2 cahce is
shared among a cluster of cores instead of being exclusive to one
single core.
To prevent oversubscription of L2 cache, load should be balanced
between such L2 clusters, especially for tasks with no shared data.
On benchmark such as SPECrate mcf test, this change provides a
boost to performance especially on medium load system on Jacobsville.
on a Jacobsville that has 24 Atom cores, arranged into 6 clusters
of 4 cores each, the benchmark number is as follow:
Improvement over baseline kernel for mcf_r
copies run time base rate
1 -0.1% -0.2%
6 25.1% 25.1%
12 18.8% 19.0%
24 0.3% 0.3%
So this looks pretty good. In terms of the system's task distribution,
some pretty bad clumping can be seen for the vanilla kernel without
the L2 cluster domain for the 6 and 12 copies case. With the extra
domain for cluster, the load does get evened out between the clusters.
Note this patch isn't an universal win as spreading isn't necessarily
a win, particually for those workload who can benefit from packing.
Signed-off-by: Tim Chen <[email protected]>
Signed-off-by: Barry Song <[email protected]>
---
arch/x86/Kconfig | 8 ++++++
arch/x86/include/asm/smp.h | 7 ++++++
arch/x86/include/asm/topology.h | 3 +++
arch/x86/kernel/cpu/cacheinfo.c | 1 +
arch/x86/kernel/cpu/common.c | 3 +++
arch/x86/kernel/smpboot.c | 44 ++++++++++++++++++++++++++++++++-
6 files changed, 65 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 88fb922c23a0..e97356e99bbe 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -996,6 +996,14 @@ config NR_CPUS
This is purely to save memory: each supported CPU adds about 8KB
to the kernel image.
+config SCHED_CLUSTER
+ bool "Cluster scheduler support"
+ default n
+ help
+ Cluster scheduler support improves the CPU scheduler's decision
+ making when dealing with machines that have clusters of CPUs
+ sharing L2 cache. If unsure say N here.
+
config SCHED_SMT
def_bool y if SMP
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 630ff08532be..08b0e90623ad 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -16,7 +16,9 @@ DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_map);
DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_die_map);
/* cpus sharing the last level cache: */
DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
+DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_l2c_shared_map);
DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id);
+DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_l2c_id);
DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);
static inline struct cpumask *cpu_llc_shared_mask(int cpu)
@@ -24,6 +26,11 @@ static inline struct cpumask *cpu_llc_shared_mask(int cpu)
return per_cpu(cpu_llc_shared_map, cpu);
}
+static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
+{
+ return per_cpu(cpu_l2c_shared_map, cpu);
+}
+
DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid);
DECLARE_EARLY_PER_CPU_READ_MOSTLY(u32, x86_cpu_to_acpiid);
DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid);
diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 9239399e5491..2548d824f103 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -103,17 +103,20 @@ static inline void setup_node_to_cpumask_map(void) { }
#include <asm-generic/topology.h>
extern const struct cpumask *cpu_coregroup_mask(int cpu);
+extern const struct cpumask *cpu_clustergroup_mask(int cpu);
#define topology_logical_package_id(cpu) (cpu_data(cpu).logical_proc_id)
#define topology_physical_package_id(cpu) (cpu_data(cpu).phys_proc_id)
#define topology_logical_die_id(cpu) (cpu_data(cpu).logical_die_id)
#define topology_die_id(cpu) (cpu_data(cpu).cpu_die_id)
+#define topology_cluster_id(cpu) (per_cpu(cpu_l2c_id, cpu))
#define topology_core_id(cpu) (cpu_data(cpu).cpu_core_id)
extern unsigned int __max_die_per_package;
#ifdef CONFIG_SMP
#define topology_die_cpumask(cpu) (per_cpu(cpu_die_map, cpu))
+#define topology_cluster_cpumask(cpu) (cpu_clustergroup_mask(cpu))
#define topology_core_cpumask(cpu) (per_cpu(cpu_core_map, cpu))
#define topology_sibling_cpumask(cpu) (per_cpu(cpu_sibling_map, cpu))
diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index d66af2950e06..3528987fef1d 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -846,6 +846,7 @@ void init_intel_cacheinfo(struct cpuinfo_x86 *c)
l2 = new_l2;
#ifdef CONFIG_SMP
per_cpu(cpu_llc_id, cpu) = l2_id;
+ per_cpu(cpu_l2c_id, cpu) = l2_id;
#endif
}
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 64b805bd6a54..38871f114af1 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -79,6 +79,9 @@ EXPORT_SYMBOL(smp_num_siblings);
/* Last level cache ID of each logical CPU */
DEFINE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id) = BAD_APICID;
+/* L2 cache ID of each logical CPU */
+DEFINE_PER_CPU_READ_MOSTLY(u16, cpu_l2c_id) = BAD_APICID;
+
/* correctly size the local cpu masks */
void __init setup_cpu_local_masks(void)
{
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 9320285a5e29..5832c6b6348f 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -101,6 +101,8 @@ EXPORT_PER_CPU_SYMBOL(cpu_die_map);
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
+DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_l2c_shared_map);
+
/* Per CPU bogomips and other parameters */
DEFINE_PER_CPU_READ_MOSTLY(struct cpuinfo_x86, cpu_info);
EXPORT_PER_CPU_SYMBOL(cpu_info);
@@ -464,6 +466,21 @@ static bool match_die(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
return false;
}
+static bool match_l2c(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
+{
+ int cpu1 = c->cpu_index, cpu2 = o->cpu_index;
+
+ /* Do not match if we do not have a valid APICID for cpu: */
+ if (per_cpu(cpu_l2c_id, cpu1) == BAD_APICID)
+ return false;
+
+ /* Do not match if L2 cache id does not match: */
+ if (per_cpu(cpu_l2c_id, cpu1) != per_cpu(cpu_l2c_id, cpu2))
+ return false;
+
+ return topology_sane(c, o, "l2c");
+}
+
/*
* Unlike the other levels, we do not enforce keeping a
* multicore group inside a NUMA node. If this happens, we will
@@ -523,7 +540,7 @@ static bool match_llc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
}
-#if defined(CONFIG_SCHED_SMT) || defined(CONFIG_SCHED_MC)
+#if defined(CONFIG_SCHED_SMT) || defined(CONFIG_SCHED_CLUSTER) || defined(CONFIG_SCHED_MC)
static inline int x86_sched_itmt_flags(void)
{
return sysctl_sched_itmt_enabled ? SD_ASYM_PACKING : 0;
@@ -541,12 +558,21 @@ static int x86_smt_flags(void)
return cpu_smt_flags() | x86_sched_itmt_flags();
}
#endif
+#ifdef CONFIG_SCHED_CLUSTER
+static int x86_cluster_flags(void)
+{
+ return cpu_cluster_flags() | x86_sched_itmt_flags();
+}
+#endif
#endif
static struct sched_domain_topology_level x86_numa_in_package_topology[] = {
#ifdef CONFIG_SCHED_SMT
{ cpu_smt_mask, x86_smt_flags, SD_INIT_NAME(SMT) },
#endif
+#ifdef CONFIG_SCHED_CLUSTER
+ { cpu_clustergroup_mask, x86_cluster_flags, SD_INIT_NAME(CLS) },
+#endif
#ifdef CONFIG_SCHED_MC
{ cpu_coregroup_mask, x86_core_flags, SD_INIT_NAME(MC) },
#endif
@@ -557,6 +583,9 @@ static struct sched_domain_topology_level x86_topology[] = {
#ifdef CONFIG_SCHED_SMT
{ cpu_smt_mask, x86_smt_flags, SD_INIT_NAME(SMT) },
#endif
+#ifdef CONFIG_SCHED_CLUSTER
+ { cpu_clustergroup_mask, x86_cluster_flags, SD_INIT_NAME(CLS) },
+#endif
#ifdef CONFIG_SCHED_MC
{ cpu_coregroup_mask, x86_core_flags, SD_INIT_NAME(MC) },
#endif
@@ -584,6 +613,7 @@ void set_cpu_sibling_map(int cpu)
if (!has_mp) {
cpumask_set_cpu(cpu, topology_sibling_cpumask(cpu));
cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
+ cpumask_set_cpu(cpu, cpu_l2c_shared_mask(cpu));
cpumask_set_cpu(cpu, topology_core_cpumask(cpu));
cpumask_set_cpu(cpu, topology_die_cpumask(cpu));
c->booted_cores = 1;
@@ -602,6 +632,9 @@ void set_cpu_sibling_map(int cpu)
if ((i == cpu) || (has_mp && match_llc(c, o)))
link_mask(cpu_llc_shared_mask, cpu, i);
+ if ((i == cpu) || (has_mp && match_l2c(c, o)))
+ link_mask(cpu_l2c_shared_mask, cpu, i);
+
if ((i == cpu) || (has_mp && match_die(c, o)))
link_mask(topology_die_cpumask, cpu, i);
}
@@ -649,6 +682,11 @@ const struct cpumask *cpu_coregroup_mask(int cpu)
return cpu_llc_shared_mask(cpu);
}
+const struct cpumask *cpu_clustergroup_mask(int cpu)
+{
+ return cpu_l2c_shared_mask(cpu);
+}
+
static void impress_friends(void)
{
int cpu;
@@ -1332,6 +1370,7 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL);
zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
+ zalloc_cpumask_var(&per_cpu(cpu_l2c_shared_map, i), GFP_KERNEL);
}
/*
@@ -1556,7 +1595,10 @@ static void remove_siblinginfo(int cpu)
cpumask_clear_cpu(cpu, topology_sibling_cpumask(sibling));
for_each_cpu(sibling, cpu_llc_shared_mask(cpu))
cpumask_clear_cpu(cpu, cpu_llc_shared_mask(sibling));
+ for_each_cpu(sibling, cpu_l2c_shared_mask(cpu))
+ cpumask_clear_cpu(cpu, cpu_l2c_shared_mask(sibling));
cpumask_clear(cpu_llc_shared_mask(cpu));
+ cpumask_clear(cpu_l2c_shared_mask(cpu));
cpumask_clear(topology_sibling_cpumask(cpu));
cpumask_clear(topology_core_cpumask(cpu));
cpumask_clear(topology_die_cpumask(cpu));
--
2.25.1
On 8/19/21 6:30 PM, Barry Song wrote:
> From: Tim Chen <[email protected]>
>
> There are x86 CPU architectures (e.g. Jacobsville) where L2 cahce is
> shared among a cluster of cores instead of being exclusive to one
> single core.
> To prevent oversubscription of L2 cache, load should be balanced
> between such L2 clusters, especially for tasks with no shared data.
> On benchmark such as SPECrate mcf test, this change provides a
> boost to performance especially on medium load system on Jacobsville.
> on a Jacobsville that has 24 Atom cores, arranged into 6 clusters
> of 4 cores each, the benchmark number is as follow:
>
> Improvement over baseline kernel for mcf_r
> copies run time base rate
> 1 -0.1% -0.2%
> 6 25.1% 25.1%
> 12 18.8% 19.0%
> 24 0.3% 0.3%
>
> So this looks pretty good. In terms of the system's task distribution,
> some pretty bad clumping can be seen for the vanilla kernel without
> the L2 cluster domain for the 6 and 12 copies case. With the extra
> domain for cluster, the load does get evened out between the clusters.
>
> Note this patch isn't an universal win as spreading isn't necessarily
> a win, particually for those workload who can benefit from packing.
I have another patch set to make cluster scheduling selectable at run
time and boot time. Will like to see people's feed back on this patch
set first before sending that out.
Thanks.
Tim