Re: [igt-dev] [PATCH i-g-t v2 1/2] tests/intel/xe_guc_pc: Add freq-power test

[Riana Tauro <riana.tauro@intel.com>]

Hi Rodrigo

On 9/21/2023 9:28 PM, Rodrigo Vivi wrote:
> On Thu, Sep 21, 2023 at 02:25:07PM +0530, Riana Tauro wrote:
>> An assumption is that at lower frequencies,
>> not only do we run slower, but we save power compared to
>> higher frequencies.
>>
>> This test runs a spinner and sets the min and max frequencies
>> to rp0 and rpn respectively. It then checks if power consumed
>> at lower frequencies is lesser than higher frequencies.
>>
>> v2: Remove Run Type
>>      change test name (Kamil)
>>      change test documentation and comments (Vinay)
>>
>> Signed-off-by: Riana Tauro <riana.tauro@intel.com>
>> Reviewed-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
>> ---
>>   tests/intel/xe_guc_pc.c | 88 +++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 88 insertions(+)
>>
>> diff --git a/tests/intel/xe_guc_pc.c b/tests/intel/xe_guc_pc.c
>> index 0327d8e0e..2b3d08fcb 100644
>> --- a/tests/intel/xe_guc_pc.c
>> +++ b/tests/intel/xe_guc_pc.c
>> @@ -13,6 +13,7 @@
>>   
>>   #include "igt.h"
>>   #include "lib/igt_syncobj.h"
>> +#include "igt_power.h"
>>   #include "igt_sysfs.h"
>>   
>>   #include "xe_drm.h"
>> @@ -382,6 +383,82 @@ static void test_reset(int fd, int gt_id, int cycles)
>>   	}
>>   }
>>   
>> +static int cmp_u64(const void *a, const void *b)
>> +{
>> +	return (*(u64 *)a - *(u64 *)b);
>> +}
>> +
>> +static uint64_t measure_power(int fd, struct igt_power *gpu)
>> +{
>> +	struct power_sample sample[2];
>> +	uint64_t power[5];
>> +
>> +	for (int i = 0; i < 5; i++) {
>> +		igt_power_get_energy(gpu, &sample[0]);
>> +		usleep(10000); /* 10 ms */
>> +		igt_power_get_energy(gpu, &sample[1]);
>> +
>> +		power[i] = igt_power_get_mW(gpu, &sample[0], &sample[1]);
>> +	}
>> +	/* Sort in ascending order and use a triangular filter */
>> +	qsort(power, 5, sizeof(*power), cmp_u64);
>> +	return DIV_ROUND_UP(power[1] + 2 * power[2] + power[3], 4);
>> +}
>> +
>> +/**
>> + * SUBTEST: freq-power
>> + * Description: Validates power consumed at higher frequencies is more than
>> + *              power consumed at lower frequencies.
>> + */
>> +static void test_freq_power(int fd, int gt_id, struct drm_xe_engine_class_instance *hwe)
>> +{
>> +	uint32_t rp0, rpn, vm;
>> +	uint64_t ahnd;
>> +	struct igt_power gpu;
>> +	struct {
>> +		uint64_t power;
>> +		uint32_t freq;
>> +	} min, max;
>> +	igt_spin_t *spin;
>> +
>> +	/* Run for engines belonging to the gt */
>> +	if (gt_id != hwe->gt_id)
>> +		return;
>> +
>> +	igt_power_open(fd, &gpu, "gpu");
>> +
>> +	rpn = get_freq(fd, gt_id, "rpn");
>> +	rp0 = get_freq(fd, gt_id, "rp0");
>> +
>> +	vm = xe_vm_create(fd, 0, 0);
>> +	ahnd = intel_allocator_open(fd, vm, INTEL_ALLOCATOR_RELOC);
>> +	spin = igt_spin_new(fd, .ahnd = ahnd, .vm = vm, .hwe = hwe);
>> +
>> +	igt_assert(set_freq(fd, gt_id, "min", rpn) > 0);
>> +	igt_assert(set_freq(fd, gt_id, "max", rpn) > 0);
>> +	min.freq = get_freq(fd, gt_id, "act");
>> +	min.power = measure_power(fd, &gpu);
>> +
>> +	igt_assert(set_freq(fd, gt_id, "min", rp0) > 0);
>> +	igt_assert(set_freq(fd, gt_id, "max", rp0) > 0);
>> +	max.freq = get_freq(fd, gt_id, "act");
>> +	max.power = measure_power(fd, &gpu);
>> +
>> +	igt_info("Engine %s:%d  min:%lumW @ %uMHz, max:%lumW @ %uMHz\n",
>> +		 xe_engine_class_string(hwe->engine_class), hwe->engine_instance,
>> +		 min.power, min.freq, max.power, max.freq);
>> +
>> +	igt_spin_free(fd, spin);
>> +	put_ahnd(ahnd);
>> +	xe_vm_destroy(fd, vm);
>> +	igt_power_close(&gpu);
>> +
>> +	/* power@max_freq should be at least 10% greater than power@min_freq */
>> +	igt_assert_f((11 * min.power < 10 * max.power),
>> +		     "%s:%d did not conserve power when setting lower frequency!\n",
>> +		     xe_engine_class_string(hwe->engine_class), hwe->engine_instance);
> 
> What exactly are we trying to test here with this case?
> This creates an artificial KPI that might not be true for the broader range
> of SKUs and generations out there. And then when it fails what should we do?
> come here and update the test case?
This test was a port from i915 [rps-power & slpc-power]

The commit message for the i915 tests is based on an assumption

"at lower frequencies, not only do we run
  slower, but we save power compared to higher frequencies."

I went through the failures there hasn't been a fix anywhere.

But shouldn't the power consumed at lower frequencies be lesser than 
higher (removing the 10% in the above condition)?

I will drop this test if not necessary

Thanks
Riana Tauro
> 
>> +}
>> +
>>   igt_main
>>   {
>>   	struct drm_xe_engine_class_instance *hwe;
>> @@ -472,6 +549,17 @@ igt_main
>>   		}
>>   	}
>>   
>> +	igt_describe("Validate more power is consumed at higher frequencies");
>> +	igt_subtest("freq-power") {
>> +		/* FIXME: Remove skip once hwmon is added */
>> +		igt_skip_on(xe_has_vram(fd));
>> +		xe_for_each_gt(fd, gt) {
>> +			xe_for_each_hw_engine(fd, hwe) {
>> +				test_freq_power(fd, gt, hwe);
>> +			}
>> +		}
>> +	}
>> +
>>   	igt_fixture {
>>   		xe_for_each_gt(fd, gt) {
>>   			set_freq(fd, gt, "min", stash_min);
>> -- 
>> 2.40.0
>>