On 2024/8/16 23:55, Dietmar Eggemann wrote:
> On 06/08/2024 10:53, Yicong Yang wrote:
>> From: Yicong Yang <yangyic...@hisilicon.com>
>>
>> On building the topology from the devicetree, we've already
>> gotten the SMT thread number of each core. Update the largest
>> SMT thread number to enable the SMT control.
>
> Do we have SMT Device Tree (DT) systems out there? But you right that DT
> at least supports SMT.
>
My system's based on ACPI. For DT part it's emulated and tested on the QEMU VM.
>> Signed-off-by: Yicong Yang <yangyic...@hisilicon.com>
>> ---
>> drivers/base/arch_topology.c | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
>> index 75fcb75d5515..95513abd664f 100644
>> --- a/drivers/base/arch_topology.c
>> +++ b/drivers/base/arch_topology.c
>> @@ -11,6 +11,7 @@
>> #include <linux/cleanup.h>
>> #include <linux/cpu.h>
>> #include <linux/cpufreq.h>
>> +#include <linux/cpu_smt.h>
>> #include <linux/device.h>
>> #include <linux/of.h>
>> #include <linux/slab.h>
>> @@ -531,6 +532,16 @@ static int __init get_cpu_for_node(struct device_node
>> *node)
>> return cpu;
>> }
>>
>> +static void __init update_smt_num_threads(unsigned int num_threads)
>> +{
>> + static unsigned int max_smt_thread_num = 1;
>> +
>> + if (num_threads > max_smt_thread_num) {
>> + max_smt_thread_num = num_threads;
>> + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num);
>> + }
>
> This could theoretically (unlikely though) call
> cpu_smt_set_num_threads() multiple times (on heterogeneous systems with
> different numbers of SMT threads).
Yes indeed. Was doing this purposely since I think this doing nothing
unexpectedly but
only update the max threads recorded in the framework.
>> +}
>> +
>> static int __init parse_core(struct device_node *core, int package_id,
>> int cluster_id, int core_id)
>> {
>> @@ -561,6 +572,8 @@ static int __init parse_core(struct device_node *core,
>> int package_id,
>> i++;
>> } while (1);
>>
>> + update_smt_num_threads(i);
>> +
>> cpu = get_cpu_for_node(core);
>> if (cpu >= 0) {
>> if (!leaf) {
>
> Why not simply do this:
>
> -->8--
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 75fcb75d5515..806537419715 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -30,6 +30,7 @@ static struct cpumask scale_freq_counters_mask;
> static bool scale_freq_invariant;
> DEFINE_PER_CPU(unsigned long, capacity_freq_ref) = 1;
> EXPORT_PER_CPU_SYMBOL_GPL(capacity_freq_ref);
> +static unsigned int max_smt_thread_num = 1;
>
This fine with me and this avoid calling cpu_smt_set_num_threads() multiple
times. We can switch to this implementation.
Thanks.
> static bool supports_scale_freq_counters(const struct cpumask *cpus)
> {
> @@ -577,6 +578,9 @@ static int __init parse_core(struct device_node *core,
> int package_id,
> return -EINVAL;
> }
>
> + if (max_smt_thread_num < i)
> + max_smt_thread_num = i;
> +
> return 0;
> }
>
> @@ -673,6 +677,9 @@ static int __init parse_socket(struct device_node *socket)
> if (!has_socket)
> ret = parse_cluster(socket, 0, -1, 0);
>
> + if (max_smt_thread_num > 1)
> + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num);
> +
> return ret;
> }
>
>
> .
>
