| Message ID | 20241030125415.18994-4-yangyicong@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Support SMT control on arm64 | expand |
On 10/30/24 13:54, 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. If a homogeneous system's using ACPI 6.2 or later, > all the CPUs should be under the root node of PPTT. There'll be > only one entry in the xarray and all the CPUs in the system will > be assumed 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 | 57 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 57 insertions(+) > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > index 1a2c72f3e7f8..47f838d6e823 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 +39,28 @@ static bool __init acpi_cpu_is_threaded(int cpu) > return !!is_threaded; > } > > +struct cpu_smt_info { > + int thread_num; > + int core_id; > +}; > + > /* > * 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 +70,32 @@ 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; > + > + /* > + * 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. > + * See the comment of find_acpi_cpu_topology_hetero_id() > + * for more details. > + * > + * 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->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 +106,24 @@ 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 (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); > + } I think you need to check that max_smt_thread_num !=0, like in the DT path. Otherwise on a platform with no SMT, max_smt_thread_num = 0 and I hit: kernel/cpu::cpu_smt_set_num_threads() WARN_ON(!num_threads || (num_threads > max_threads)); -> if (max_smt_thread_num) cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); > + > + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); > + xa_destroy(&hetero_cpu); > return 0; > } > #endif
On 2024/11/8 1:20, Pierre Gondois wrote: > > > On 10/30/24 13:54, 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. If a homogeneous system's using ACPI 6.2 or later, >> all the CPUs should be under the root node of PPTT. There'll be >> only one entry in the xarray and all the CPUs in the system will >> be assumed 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 | 57 ++++++++++++++++++++++++++++++++++++ >> 1 file changed, 57 insertions(+) >> [...] >> @@ -67,6 +106,24 @@ 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 (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); >> + } > > I think you need to check that max_smt_thread_num !=0, > like in the DT path. Otherwise on a platform with no SMT, > max_smt_thread_num = 0 and I hit: > > kernel/cpu::cpu_smt_set_num_threads() > WARN_ON(!num_threads || (num_threads > max_threads)); > > > -> > if (max_smt_thread_num) > cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); > sorry for this silly mistake. yes we should do the same like in the DT path. I'll get this fixed. thanks for testing. >> + >> + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); >> + xa_destroy(&hetero_cpu); >> return 0; >> } >> #endif > > .
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index 1a2c72f3e7f8..47f838d6e823 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 +39,28 @@ static bool __init acpi_cpu_is_threaded(int cpu) return !!is_threaded; } +struct cpu_smt_info { + int thread_num; + int core_id; +}; + /* * 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 +70,32 @@ 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; + + /* + * 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. + * See the comment of find_acpi_cpu_topology_hetero_id() + * for more details. + * + * 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->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 +106,24 @@ 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 (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