Re: [PATCH v7 6/6] cpufreq: powernv: Add sysfs attributes to show throttle stats

Viresh Kumar
2016-01-28T11:41:19Z

On 28-01-16, 12:55, Shilpasri G Bhat wrote:
> Create sysfs attributes to export throttle information in
> /sys/devices/system/cpu/cpufreq/chipN. The newly added sysfs files are as
> follows:
>
> 1)/sys/devices/system/cpu/cpufreq/chip0/throttle_frequencies
> This gives the throttle stats for each of the available frequencies.
> The throttle stat of a frequency is the total number of times the max
> frequency is reduced to that frequency.
> # cat /sys/devices/system/cpu/cpufreq/chip0/throttle_frequencies
> 4023000 0
> 3990000 0
> 3956000 1
> 3923000 0
> 3890000 0
> 3857000 2
> 3823000 0
> 3790000 0
> 3757000 2
> 3724000 1
> 3690000 1
> ...
>
> 2)/sys/devices/system/cpu/cpufreq/chip0/throttle_reasons
> This directory contains throttle reason files. Each file gives the
> total number of times the max frequency is throttled, except for
> 'unthrottle_count', which gives the total number of times the max
> frequency is unthrottled after being throttled.
> # cd /sys/devices/system/cpu/cpufreq/chip0/throttle_reasons
> # cat cpu_over_temperature
> 7
> # cat occ_reset
> 0
> # cat over_current
> 0
> # cat power_cap
> 0
> # cat power_supply_failure
> 0
> # cat unthrottle_count
> 7

Wouldn't it be better to keep a two dimensional table here, something
like: trans_table ?

You can have "reasons" in the vertical dimension and frequencies in
the horizontal one? So, that user can see which frequencies got
throttled and why?

> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
> index b683e8e..dea4620 100644
> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
> @@ -271,3 +271,48 @@ Description: Parameters for the CPU cache attributes
> - WriteBack: data is written only to the cache line and
> the modified cache line is written to main
> memory only when it is replaced
> +
> +What: /sys/devices/system/cpu/cpufreq/chip*/throttle_stats

You need documentation for chip*/ as well..

And how can a user know which policies or CPUs belong to a chip?

> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> static struct chip {
> unsigned int id;
> bool throttled;
> @@ -62,6 +72,11 @@ static struct chip {
> u8 throttle_reason;
> cpumask_t mask;
> struct work_struct throttle;
> + int throttle_turbo;
> + int throttle_nominal;
> + int reason[OCC_MAX_REASON];
> + int *pstate_stat;
> + struct kobject *kobj;
> } *chips;
>
> static int nr_chips;
> @@ -196,6 +211,126 @@ static struct freq_attr *powernv_cpu_freq_attr[] = {
> NULL,
> };
>
> +static inline int get_chip_index(unsigned int id)
> +{
> + int i;
> +
> + for (i = 0; i < nr_chips; i++)
> + if (chips[i].id == id)
> + return i;
> +
> + return -EINVAL;
> +}
> +
> +static inline int get_chip_index_from_kobj(struct kobject *kobj)
> +{
> + int ret, id;
> + int len = strlen("chip");
> +
> + ret = kstrtoint(kobj->name + len, 0, &id);

That doesn't look nice. What about keeping the kobject in the 'struct
chip' and using container of here?

You can register the kobject with: kobject_init_and_add().

> + if (ret)
> + return ret;
> +
> + ret = get_chip_index(id);
> + if (ret < 0)
> + pr_warn_once("%s Matching chip-id not found %d\n", __func__,
> + id);
> + return ret;
> +}
> +
> +static ssize_t throttle_freq_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + int i, count = 0, id;
> +
> + id = get_chip_index_from_kobj(kobj);
> + if (id < 0)
> + return id;
> +
> + for (i = 0; i < powernv_pstate_info.nr_pstates; i++)
> + count += sprintf(&buf[count], "%d %d\n",
> + powernv_freqs[i].frequency,
> + chips[id].pstate_stat[i]);
> +
> + return count;
> +}
> +
> +static struct kobj_attribute attr_throttle_frequencies =
> +__ATTR(throttle_frequencies, 0444, throttle_freq_show, NULL);

Use DEVICE_ATTR_RO macro ?

> @@ -583,12 +736,38 @@ static int init_chip_info(void)
> goto free_chip_map;
>
> for (i = 0; i < nr_chips; i++) {
> + char name[10];
> +
> chips[i].id = chip[i];
> cpumask_copy(&chips[i].mask, cpumask_of_node(chip[i]));
> INIT_WORK(&chips[i].throttle, powernv_cpufreq_work_fn);
> + chips[i].pstate_stat = kcalloc(powernv_pstate_info.nr_pstates,
> + sizeof(int), GFP_KERNEL);
> + if (!chips[i].pstate_stat)
> + goto free;
> +
> + sprintf(name, "chip%d", chips[i].id);

Always use snprintf ..

> + chips[i].kobj = kobject_create_and_add(name,
> + cpufreq_global_kobject);
> + if (!chips[i].kobj)
> + goto free;
> +
> + ret = sysfs_create_groups(chips[i].kobj, throttle_attr_groups);
> + if (ret) {
> + pr_info("Chip %d failed to create throttle sysfs group\n",
> + chips[i].id);
> + goto free;
> + }
> }
>
> return 0;
> +free:
> + nr_chips = i;
> + for (i = 0; i <= nr_chips; i++) {

Rather do:

while (--i >= 0) {
kobject_put(chips[i].kobj);
kfree(chips[i].pstate_stat);
}

> + kobject_put(chips[i].kobj);
> + kfree(chips[i].pstate_stat);

You haven't removed the sysfs-group. Also make sure you aren't trying
to free/remove resources you haven't allocated, as the earlier part
can fail after 3 different allocations and you are doing same thing
here for all of them.

> + }
> + kfree(chips);
> free_chip_map:
> kfree(core_to_chip_map);
> out:
> @@ -623,9 +802,17 @@ module_init(powernv_cpufreq_init);
>
> static void __exit powernv_cpufreq_exit(void)
> {
> + int i;
> +
> unregister_reboot_notifier(&powernv_cpufreq_reboot_nb);
> opal_message_notifier_unregister(OPAL_MSG_OCC,
> &powernv_cpufreq_opal_nb);
> +
> + for (i = 0; i < nr_chips; i++) {
> + kobject_put(chips[i].kobj);

remove groups ?

> + kfree(chips[i].pstate_stat);
> + }
> +
> kfree(chips);
> kfree(core_to_chip_map);
> cpufreq_unregister_driver(&powernv_cpufreq_driver);
> --
> 1.9.3

--
viresh