On 21/05/15 10:39, Huaitong Han wrote:
> When checking the ACPI funciton of C-status, after 100 seconds sleep,
> the sampling value of C0 status from the xenpm tool decreases.
> Because C0=NOW()-C1-C2-C3-C4, when NOW() value is during idle time,
> NOW() value is bigger than last C-status update time, and C0 value
> is also bigger than ture value. if margin of the second error cannot
> make up for margin of the first error, the value of C0 would decrease.
>
> Signed-off-by: Huaitong Han <huaitong....@intel.com>
>
> static void print_acpi_power(uint32_t cpu, struct acpi_processor_power
> *power)
> {
> - uint32_t i, idle_usage = 0;
> - uint64_t res, idle_res = 0;
> - u32 usage;
> + uint64_t idle_res = 0, idle_usage = 0;
> + uint64_t last_state_update_tick, current_tick, current_stime;
> + uint64_t usage[ACPI_PROCESSOR_MAX_POWER] = { 0 };
> + uint64_t res_tick[ACPI_PROCESSOR_MAX_POWER] = { 0 };
> + unsigned int i;
> u8 last_state_idx;
>
> printk("==cpu%d==\n", cpu);
> @@ -264,28 +286,37 @@ static void print_acpi_power(uint32_t cpu, struct
> acpi_processor_power *power)
> printk("active state:\t\tC%d\n", last_state_idx);
> printk("max_cstate:\t\tC%d\n", max_cstate);
> printk("states:\n");
> -
> +
> + spin_lock_irq(&power->stat_lock);
> + current_tick = cpuidle_get_tick();
> + current_stime = NOW();
> for ( i = 1; i < power->count; i++ )
> {
> - spin_lock_irq(&power->stat_lock);
> - res = tick_to_ns(power->states[i].time);
> - usage = power->states[i].usage;
> - spin_unlock_irq(&power->stat_lock);
> + res_tick[i] = power->states[i].time;
> + usage[i] = power->states[i].usage;
> + }
> + last_state_update_tick = power->last_state_update_tick;
> + spin_unlock_irq(&power->stat_lock);
>
> - idle_usage += usage;
> - idle_res += res;
> + res_tick[last_state_idx] += ticks_elapsed(last_state_update_tick,
> current_tick);
> + usage[last_state_idx]++;
These two arrays get used with last_state_idx as -1, which underflows to
256.
Please see about fixing, or we can see about reverting if you can't get
to it quickly.
~Andrew
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