From: Yicong Yang <yangyicong@hisilicon.com>
For ACPI we'll build the topology from PPTT and we cannot directly
get the SMT number of each core. Instead using a temporary xarray
to record the heterogeneous information (from ACPI_PPTT_ACPI_IDENTICAL)
and SMT information of the first core in its heterogeneous CPU cluster
when building the topology. Then we can know the largest SMT number
in the system.
The core's SMT control provides two interface to the users [1]:
1) enable/disable SMT by writing on/off
2) enable/disable SMT by writing thread number 1/max_thread_number
If a system have more than one SMT thread number the 2) may
not handle it well, since there're multiple thread numbers in the
system and 2) only accept 1/max_thread_number. So issue a warning
to notify the users if such system detected.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/testing/sysfs-devices-system-cpu#n542
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
---
arch/arm64/kernel/topology.c | 61 ++++++++++++++++++++++++++++++++++++
1 file changed, 61 insertions(+)
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 1a2c72f3e7f8..2fa584b932ee 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -15,8 +15,10 @@
#include <linux/arch_topology.h>
#include <linux/cacheinfo.h>
#include <linux/cpufreq.h>
+#include <linux/cpu_smt.h>
#include <linux/init.h>
#include <linux/percpu.h>
+#include <linux/xarray.h>
#include <asm/cpu.h>
#include <asm/cputype.h>
@@ -37,17 +39,29 @@ static bool __init acpi_cpu_is_threaded(int cpu)
return !!is_threaded;
}
+struct cpu_smt_info {
+ int thread_num;
+ int core_id;
+ int cpu;
+};
+
/*
* Propagate the topology information of the processor_topology_node tree to the
* cpu_topology array.
*/
int __init parse_acpi_topology(void)
{
+ int max_smt_thread_num = 0;
+ struct cpu_smt_info *entry;
+ struct xarray hetero_cpu;
+ unsigned long hetero_id;
int cpu, topology_id;
if (acpi_disabled)
return 0;
+ xa_init(&hetero_cpu);
+
for_each_possible_cpu(cpu) {
topology_id = find_acpi_cpu_topology(cpu, 0);
if (topology_id < 0)
@@ -57,6 +71,30 @@ int __init parse_acpi_topology(void)
cpu_topology[cpu].thread_id = topology_id;
topology_id = find_acpi_cpu_topology(cpu, 1);
cpu_topology[cpu].core_id = topology_id;
+
+ /*
+ * Build up the XArray using the heterogeneous ID of
+ * the CPU cluster. Store the CPU and SMT information
+ * of the first appeared CPU in the CPU cluster of this
+ * heterogeneous ID since the SMT information should be
+ * the same in this CPU cluster. Then we can know the
+ * SMT information of each heterogeneous CPUs in the
+ * system.
+ */
+ hetero_id = find_acpi_cpu_topology_hetero_id(cpu);
+ entry = (struct cpu_smt_info *)xa_load(&hetero_cpu, hetero_id);
+ if (!entry) {
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ WARN_ON(!entry);
+
+ entry->cpu = cpu;
+ entry->core_id = topology_id;
+ entry->thread_num = 1;
+ xa_store(&hetero_cpu, hetero_id,
+ entry, GFP_KERNEL);
+ } else if (entry->core_id == topology_id) {
+ entry->thread_num++;
+ }
} else {
cpu_topology[cpu].thread_id = -1;
cpu_topology[cpu].core_id = topology_id;
@@ -67,6 +105,29 @@ int __init parse_acpi_topology(void)
cpu_topology[cpu].package_id = topology_id;
}
+ /*
+ * This should be a short loop depending on the number of heterogeneous
+ * CPU clusters. Typically on a homogeneous system there's only one
+ * entry in the XArray.
+ */
+ xa_for_each(&hetero_cpu, hetero_id, entry) {
+ /*
+ * If max_smt_thread_num has been initialized and doesn't match
+ * the thread number of this entry, then the system has
+ * heterogeneous SMT topology.
+ */
+ if (entry->thread_num != max_smt_thread_num && max_smt_thread_num)
+ pr_warn_once("Heterogeneous SMT topology is partly supported by SMT control\n");
+
+ if (entry->thread_num > max_smt_thread_num)
+ max_smt_thread_num = entry->thread_num;
+
+ xa_erase(&hetero_cpu, hetero_id);
+ kfree(entry);
+ }
+
+ cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num);
+ xa_destroy(&hetero_cpu);
return 0;
}
#endif
--
2.24.0
Hello Yicong, On 10/15/24 04:18, Yicong Yang wrote: > From: Yicong Yang <yangyicong@hisilicon.com> > > For ACPI we'll build the topology from PPTT and we cannot directly > get the SMT number of each core. Instead using a temporary xarray > to record the heterogeneous information (from ACPI_PPTT_ACPI_IDENTICAL) > and SMT information of the first core in its heterogeneous CPU cluster > when building the topology. Then we can know the largest SMT number > in the system. Is it possible to also state that the logic only work for PPTT versions prior to 6.2. Otherwise find_acpi_cpu_topology_hetero_id() will return the id of the root node of the PPTT, and all the CPUs of the platform will be assumed to be identical. > > The core's SMT control provides two interface to the users [1]: > 1) enable/disable SMT by writing on/off > 2) enable/disable SMT by writing thread number 1/max_thread_number > > If a system have more than one SMT thread number the 2) may > not handle it well, since there're multiple thread numbers in the > system and 2) only accept 1/max_thread_number. So issue a warning > to notify the users if such system detected. > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/testing/sysfs-devices-system-cpu#n542 > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> > --- > arch/arm64/kernel/topology.c | 61 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 61 insertions(+) > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > index 1a2c72f3e7f8..2fa584b932ee 100644 > --- a/arch/arm64/kernel/topology.c > +++ b/arch/arm64/kernel/topology.c > @@ -15,8 +15,10 @@ > #include <linux/arch_topology.h> > #include <linux/cacheinfo.h> > #include <linux/cpufreq.h> > +#include <linux/cpu_smt.h> > #include <linux/init.h> > #include <linux/percpu.h> > +#include <linux/xarray.h> > > #include <asm/cpu.h> > #include <asm/cputype.h> > @@ -37,17 +39,29 @@ static bool __init acpi_cpu_is_threaded(int cpu) > return !!is_threaded; > } > > +struct cpu_smt_info { > + int thread_num; > + int core_id; > + int cpu; It doesn't seem that the 'cpu' is used. Maybe this should be removed, or used in the error message (I think this could be removed). > +}; > + > /* > * Propagate the topology information of the processor_topology_node tree to the > * cpu_topology array. > */ > int __init parse_acpi_topology(void) > { > + int max_smt_thread_num = 0; > + struct cpu_smt_info *entry; > + struct xarray hetero_cpu; > + unsigned long hetero_id; > int cpu, topology_id; > > if (acpi_disabled) > return 0; > > + xa_init(&hetero_cpu); > + > for_each_possible_cpu(cpu) { > topology_id = find_acpi_cpu_topology(cpu, 0); > if (topology_id < 0) > @@ -57,6 +71,30 @@ int __init parse_acpi_topology(void) > cpu_topology[cpu].thread_id = topology_id; > topology_id = find_acpi_cpu_topology(cpu, 1); > cpu_topology[cpu].core_id = topology_id; > + > + /* > + * Build up the XArray using the heterogeneous ID of > + * the CPU cluster. Store the CPU and SMT information > + * of the first appeared CPU in the CPU cluster of this > + * heterogeneous ID since the SMT information should be > + * the same in this CPU cluster. Then we can know the > + * SMT information of each heterogeneous CPUs in the > + * system. > + */ A suggestion just in case: /* * In the PPTT, CPUs below a node with the 'identical * implementation' flag have the same number of threads. * Count the number of threads for only one CPU (i.e. * one core_id) among those with the same hetero_id. * * One entry is created for each node having: * - the 'identical implementation' flag * - its parent not having the flag */ > + hetero_id = find_acpi_cpu_topology_hetero_id(cpu); > + entry = (struct cpu_smt_info *)xa_load(&hetero_cpu, hetero_id); > + if (!entry) { > + entry = kzalloc(sizeof(*entry), GFP_KERNEL); > + WARN_ON(!entry); > + > + entry->cpu = cpu; > + entry->core_id = topology_id; > + entry->thread_num = 1; > + xa_store(&hetero_cpu, hetero_id, > + entry, GFP_KERNEL); > + } else if (entry->core_id == topology_id) { > + entry->thread_num++; > + } > } else { > cpu_topology[cpu].thread_id = -1; > cpu_topology[cpu].core_id = topology_id; > @@ -67,6 +105,29 @@ int __init parse_acpi_topology(void) > cpu_topology[cpu].package_id = topology_id; > } > > + /* > + * This should be a short loop depending on the number of heterogeneous > + * CPU clusters. Typically on a homogeneous system there's only one > + * entry in the XArray. > + */ I think it should be ok to remove the above/below comments > + xa_for_each(&hetero_cpu, hetero_id, entry) { > + /* > + * If max_smt_thread_num has been initialized and doesn't match > + * the thread number of this entry, then the system has > + * heterogeneous SMT topology. > + */ > + if (entry->thread_num != max_smt_thread_num && max_smt_thread_num) > + pr_warn_once("Heterogeneous SMT topology is partly supported by SMT control\n"); > + > + if (entry->thread_num > max_smt_thread_num) > + max_smt_thread_num = entry->thread_num; > + > + xa_erase(&hetero_cpu, hetero_id); > + kfree(entry); > + } > + > + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); > + xa_destroy(&hetero_cpu); > return 0; > } > #endif Otherwise I tested the SMT detection and it worked well
On 2024/10/24 16:44, Pierre Gondois wrote: > Hello Yicong, > > On 10/15/24 04:18, Yicong Yang wrote: >> From: Yicong Yang <yangyicong@hisilicon.com> >> >> For ACPI we'll build the topology from PPTT and we cannot directly >> get the SMT number of each core. Instead using a temporary xarray >> to record the heterogeneous information (from ACPI_PPTT_ACPI_IDENTICAL) >> and SMT information of the first core in its heterogeneous CPU cluster >> when building the topology. Then we can know the largest SMT number >> in the system. > > Is it possible to also state that the logic only work for PPTT versions > prior to 6.2. Otherwise find_acpi_cpu_topology_hetero_id() will return > the id of the root node of the PPTT, and all the CPUs of the platform > will be assumed to be identical. > sure. of course. >> >> The core's SMT control provides two interface to the users [1]: >> 1) enable/disable SMT by writing on/off >> 2) enable/disable SMT by writing thread number 1/max_thread_number >> >> If a system have more than one SMT thread number the 2) may >> not handle it well, since there're multiple thread numbers in the >> system and 2) only accept 1/max_thread_number. So issue a warning >> to notify the users if such system detected. >> >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/testing/sysfs-devices-system-cpu#n542 >> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> >> --- >> arch/arm64/kernel/topology.c | 61 ++++++++++++++++++++++++++++++++++++ >> 1 file changed, 61 insertions(+) >> >> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c >> index 1a2c72f3e7f8..2fa584b932ee 100644 >> --- a/arch/arm64/kernel/topology.c >> +++ b/arch/arm64/kernel/topology.c >> @@ -15,8 +15,10 @@ >> #include <linux/arch_topology.h> >> #include <linux/cacheinfo.h> >> #include <linux/cpufreq.h> >> +#include <linux/cpu_smt.h> >> #include <linux/init.h> >> #include <linux/percpu.h> >> +#include <linux/xarray.h> >> #include <asm/cpu.h> >> #include <asm/cputype.h> >> @@ -37,17 +39,29 @@ static bool __init acpi_cpu_is_threaded(int cpu) >> return !!is_threaded; >> } >> +struct cpu_smt_info { >> + int thread_num; >> + int core_id; >> + int cpu; > > It doesn't seem that the 'cpu' is used. Maybe this should be removed, > or used in the error message (I think this could be removed). > sure. will remove.. >> +}; >> + >> /* >> * Propagate the topology information of the processor_topology_node tree to the >> * cpu_topology array. >> */ >> int __init parse_acpi_topology(void) >> { >> + int max_smt_thread_num = 0; >> + struct cpu_smt_info *entry; >> + struct xarray hetero_cpu; >> + unsigned long hetero_id; >> int cpu, topology_id; >> if (acpi_disabled) >> return 0; >> + xa_init(&hetero_cpu); >> + >> for_each_possible_cpu(cpu) { >> topology_id = find_acpi_cpu_topology(cpu, 0); >> if (topology_id < 0) >> @@ -57,6 +71,30 @@ int __init parse_acpi_topology(void) >> cpu_topology[cpu].thread_id = topology_id; >> topology_id = find_acpi_cpu_topology(cpu, 1); >> cpu_topology[cpu].core_id = topology_id; >> + >> + /* >> + * Build up the XArray using the heterogeneous ID of >> + * the CPU cluster. Store the CPU and SMT information >> + * of the first appeared CPU in the CPU cluster of this >> + * heterogeneous ID since the SMT information should be >> + * the same in this CPU cluster. Then we can know the >> + * SMT information of each heterogeneous CPUs in the >> + * system. >> + */ > > A suggestion just in case: > /* > * In the PPTT, CPUs below a node with the 'identical > * implementation' flag have the same number of threads. > * Count the number of threads for only one CPU (i.e. > * one core_id) among those with the same hetero_id. > * > * One entry is created for each node having: > * - the 'identical implementation' flag > * - its parent not having the flag > */ > ok maybe we can also refer to the comments of find_acpi_cpu_topology_hetero_id() [1] to lead reader there if they want more details. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/acpi/pptt.c#n794 > >> + hetero_id = find_acpi_cpu_topology_hetero_id(cpu); >> + entry = (struct cpu_smt_info *)xa_load(&hetero_cpu, hetero_id); >> + if (!entry) { >> + entry = kzalloc(sizeof(*entry), GFP_KERNEL); >> + WARN_ON(!entry); >> + >> + entry->cpu = cpu; >> + entry->core_id = topology_id; >> + entry->thread_num = 1; >> + xa_store(&hetero_cpu, hetero_id, >> + entry, GFP_KERNEL); >> + } else if (entry->core_id == topology_id) { >> + entry->thread_num++; >> + } >> } else { >> cpu_topology[cpu].thread_id = -1; >> cpu_topology[cpu].core_id = topology_id; >> @@ -67,6 +105,29 @@ int __init parse_acpi_topology(void) >> cpu_topology[cpu].package_id = topology_id; >> } >> + /* >> + * This should be a short loop depending on the number of heterogeneous >> + * CPU clusters. Typically on a homogeneous system there's only one >> + * entry in the XArray. >> + */ > > I think it should be ok to remove the above/below comments > I'd leave the above comment since this won't make people who are awared of the efficiency feel nervous about the loop here... will drop the below comment. >> + xa_for_each(&hetero_cpu, hetero_id, entry) { >> + /* >> + * If max_smt_thread_num has been initialized and doesn't match >> + * the thread number of this entry, then the system has >> + * heterogeneous SMT topology. >> + */ >> + if (entry->thread_num != max_smt_thread_num && max_smt_thread_num) >> + pr_warn_once("Heterogeneous SMT topology is partly supported by SMT control\n"); >> + >> + if (entry->thread_num > max_smt_thread_num) >> + max_smt_thread_num = entry->thread_num; >> + >> + xa_erase(&hetero_cpu, hetero_id); >> + kfree(entry); >> + } >> + >> + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); >> + xa_destroy(&hetero_cpu); >> return 0; >> } >> #endif > > Otherwise I tested the SMT detection and it worked well > appreciated for the tests! Thanks.
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