Re: [igt-dev] [PATCH i-g-t 3/3] i915/gem_exec_schedule: Measure semaphore power consumption

[Ashutosh Dixit <ashutosh.dixit@intel.com>]

On Thu, 31 Jan 2019 08:17:17 -0800, Chris Wilson wrote:
> 
> How much energy does spinning on a semaphore consume relative to plain
> old spinning?
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  tests/i915/gem_exec_schedule.c | 72 +++++++++++++++++++++++++++++++++-
>  1 file changed, 71 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/i915/gem_exec_schedule.c b/tests/i915/gem_exec_schedule.c
> index 0462ce84f..184ceb7d6 100644
> --- a/tests/i915/gem_exec_schedule.c
> +++ b/tests/i915/gem_exec_schedule.c
> @@ -29,9 +29,10 @@
>  #include <signal.h>
>  
>  #include "igt.h"
> -#include "igt_vgem.h"
> +#include "igt_gpu_power.h"
>  #include "igt_rand.h"
>  #include "igt_sysfs.h"
> +#include "igt_vgem.h"
>  #include "i915/gem_ring.h"
>  
>  #define LO 0
> @@ -1191,6 +1192,65 @@ static void test_pi_ringfull(int fd, unsigned int engine)
>  	munmap(result, 4096);
>  }
>  
> +static void measure_semaphore_power(int i915)
> +{
> +	struct gpu_power power;
> +	unsigned int engine, signaler;
> +
> +	igt_require(gpu_power_open(&power) == 0);
> +
> +	for_each_physical_engine(i915, signaler) {
> +		struct gpu_power_sample s_spin[2];
> +		struct gpu_power_sample s_sema[2];
> +		double baseline, total;
> +		int64_t jiffie = 1;
> +		igt_spin_t *spin;
> +
> +		spin = __igt_spin_batch_new(i915,
> +					    .engine = signaler,
> +					    .flags = IGT_SPIN_POLL_RUN);
> +		gem_wait(i915, spin->handle, &jiffie); /* waitboost */
> +		igt_assert(spin->running);
> +		igt_spin_busywait_until_running(spin);
> +
> +		gpu_power_read(&power, &s_spin[0]);
> +		usleep(100*1000);
> +		gpu_power_read(&power, &s_spin[1]);
> +
> +		/* Add a waiter to each engine */
> +		for_each_physical_engine(i915, engine) {
>
See the following warning now as a result of this patch, most likely the
code is incorrect too due to the shadowed variable:

ninja: Entering directory `build'
[182/621] Compiling C object 'tests/59830eb@@gem_exec_schedule@exe/i915_gem_exec_schedule.c.o'.
In file included from ../lib/igt.h:40,
                 from ../tests/i915/gem_exec_schedule.c:31:
../tests/i915/gem_exec_schedule.c: In function ‘measure_semaphore_power’:
../lib/igt_gt.h:84:44: warning: declaration of ‘e__’ shadows a previous local [-Wshadow]
  for (const struct intel_execution_engine *e__ = intel_execution_engines;\
                                            ^~~
../tests/i915/gem_exec_schedule.c:1316:3: note: in expansion of macro ‘for_each_physical_engine’
   for_each_physical_engine(i915, engine) {
   ^~~~~~~~~~~~~~~~~~~~~~~~
../lib/igt_gt.h:84:44: note: shadowed declaration is here
  for (const struct intel_execution_engine *e__ = intel_execution_engines;\
                                            ^~~
../tests/i915/gem_exec_schedule.c:1297:2: note: in expansion of macro ‘for_each_physical_engine’
  for_each_physical_engine(i915, signaler) {
  ^~~~~~~~~~~~~~~~~~~~~~~~
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