Re: [PATCH v3 4/8] drm/panfrost: Add fdinfo support GPU load metrics

[Boris Brezillon <boris.brezillon@collabora.com>]

On Tue,  5 Sep 2023 19:45:20 +0100
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> The drm-stats fdinfo tags made available to user space are drm-engine,
> drm-cycles, drm-max-freq and drm-curfreq, one per job slot.
> 
> This deviates from standard practice in other DRM drivers, where a single
> set of key:value pairs is provided for the whole render engine. However,
> Panfrost has separate queues for fragment and vertex/tiler jobs, so a
> decision was made to calculate bus cycles and workload times separately.
> 
> Maximum operating frequency is calculated at devfreq initialisation time.
> Current frequency is made available to user space because nvtop uses it
> when performing engine usage calculations.
> 
> It is important to bear in mind that both GPU cycle and kernel time numbers
> provided are at best rough estimations, and always reported in excess from
> the actual figure because of two reasons:
>  - Excess time because of the delay between the end of a job processing,
>    the subsequent job IRQ and the actual time of the sample.
>  - Time spent in the engine queue waiting for the GPU to pick up the next
>    job.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_devfreq.c |  8 +++
>  drivers/gpu/drm/panfrost/panfrost_devfreq.h |  3 ++
>  drivers/gpu/drm/panfrost/panfrost_device.h  | 13 +++++
>  drivers/gpu/drm/panfrost/panfrost_drv.c     | 59 ++++++++++++++++++++-
>  drivers/gpu/drm/panfrost/panfrost_job.c     | 27 ++++++++++
>  drivers/gpu/drm/panfrost/panfrost_job.h     |  4 ++
>  6 files changed, 113 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 58dfb15a8757..28caffc689e2 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -58,6 +58,7 @@ static int panfrost_devfreq_get_dev_status(struct device *dev,
>  	spin_lock_irqsave(&pfdevfreq->lock, irqflags);
>  
>  	panfrost_devfreq_update_utilization(pfdevfreq);
> +	pfdevfreq->current_frequency = status->current_frequency;
>  
>  	status->total_time = ktime_to_ns(ktime_add(pfdevfreq->busy_time,
>  						   pfdevfreq->idle_time));
> @@ -117,6 +118,7 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>  	struct devfreq *devfreq;
>  	struct thermal_cooling_device *cooling;
>  	struct panfrost_devfreq *pfdevfreq = &pfdev->pfdevfreq;
> +	unsigned long freq = ULONG_MAX;
>  
>  	if (pfdev->comp->num_supplies > 1) {
>  		/*
> @@ -172,6 +174,12 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>  		return ret;
>  	}
>  
> +	/* Find the fastest defined rate  */
> +	opp = dev_pm_opp_find_freq_floor(dev, &freq);
> +	if (IS_ERR(opp))
> +		return PTR_ERR(opp);
> +	pfdevfreq->fast_rate = freq;
> +
>  	dev_pm_opp_put(opp);
>  
>  	/*
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> index 1514c1f9d91c..48dbe185f206 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> @@ -19,6 +19,9 @@ struct panfrost_devfreq {
>  	struct devfreq_simple_ondemand_data gov_data;
>  	bool opp_of_table_added;
>  
> +	unsigned long current_frequency;
> +	unsigned long fast_rate;
> +
>  	ktime_t busy_time;
>  	ktime_t idle_time;
>  	ktime_t time_last_update;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 5c09c9f3ae08..7ad3973b1a3a 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -24,6 +24,7 @@ struct panfrost_perfcnt;
>  
>  #define NUM_JOB_SLOTS 3
>  #define MAX_PM_DOMAINS 5
> +#define MAX_SLOT_NAME_LEN 25
>  
>  struct panfrost_features {
>  	u16 id;
> @@ -141,12 +142,24 @@ struct panfrost_mmu {
>  	struct list_head list;
>  };
>  
> +struct drm_info_gpu {
> +	unsigned long maxfreq;
> +
> +	struct engine_info {

Uh, I'm not a huge fan of nested struct definitions. If you really need
struct engine_info, move it out of drm_info_gpu please.

> +		unsigned long long elapsed_ns;
> +		unsigned long long cycles;
> +		char name[MAX_SLOT_NAME_LEN];

I think we can drop this field (see below).

> +	} engines[NUM_JOB_SLOTS];
> +};
> +
>  struct panfrost_file_priv {
>  	struct panfrost_device *pfdev;
>  
>  	struct drm_sched_entity sched_entity[NUM_JOB_SLOTS];
>  
>  	struct panfrost_mmu *mmu;
> +
> +	struct drm_info_gpu fdinfo;
>  };
>  
>  static inline struct panfrost_device *to_panfrost_device(struct drm_device *ddev)
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 2dfd9f79a31b..94787f4aee27 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -268,6 +268,7 @@ static int panfrost_ioctl_submit(struct drm_device *dev, void *data,
>  	job->requirements = args->requirements;
>  	job->flush_id = panfrost_gpu_get_latest_flush_id(pfdev);
>  	job->mmu = file_priv->mmu;
> +	job->priv = file_priv;
>  
>  	slot = panfrost_job_get_slot(job);
>  
> @@ -484,6 +485,14 @@ panfrost_open(struct drm_device *dev, struct drm_file *file)
>  		goto err_free;
>  	}
>  
> +	snprintf(panfrost_priv->fdinfo.engines[0].name, MAX_SLOT_NAME_LEN, "fragment");
> +	snprintf(panfrost_priv->fdinfo.engines[1].name, MAX_SLOT_NAME_LEN, "vertex-tiler");
> +/* Not exposed to userspace yet */
> +#if 0
> +	snprintf(panfrost_priv->fdinfo.engines[2].name, MAX_SLOT_NAME_LEN, "compute-only");
> +#endif
> +	panfrost_priv->fdinfo.maxfreq = pfdev->pfdevfreq.fast_rate;
> +
>  	ret = panfrost_job_open(panfrost_priv);
>  	if (ret)
>  		goto err_job;
> @@ -524,7 +533,54 @@ static const struct drm_ioctl_desc panfrost_drm_driver_ioctls[] = {
>  	PANFROST_IOCTL(MADVISE,		madvise,	DRM_RENDER_ALLOW),
>  };
>  
> -DEFINE_DRM_GEM_FOPS(panfrost_drm_driver_fops);
> +
> +static void panfrost_gpu_show_fdinfo(struct panfrost_device *pfdev,
> +				     struct panfrost_file_priv *panfrost_priv,
> +				     struct drm_printer *p)
> +{
> +	int i;
> +
> +	/*
> +	 * IMPORTANT NOTE: drm-cycles and drm-engine measurements are not
> +	 * accurate, as they only provide a rough estimation of the number of
> +	 * GPU cycles and CPU time spent in a given context. This is due to two
> +	 * different factors:
> +	 * - Firstly, we must consider the time the CPU and then the kernel
> +	 *   takes to process the GPU interrupt, which means additional time and
> +	 *   GPU cycles will be added in excess to the real figure.
> +	 * - Secondly, the pipelining done by the Job Manager (2 job slots per
> +	 *   engine) implies there is no way to know exactly how much time each
> +	 *   job spent on the GPU.
> +	 */
> +
> +	for (i = 0; i < NUM_JOB_SLOTS - 1; i++) {
> +		struct engine_info *ei = &panfrost_priv->fdinfo.engines[i];

I'd drop the name field in engine_info and add a

		static const char *names[] = {
			"fragment", "vertex-tiler", "compute-only"
		};

and then just use names[i] to get the engine name.

> +
> +		drm_printf(p, "drm-engine-%s:\t%llu ns\n",
> +			   ei->name, ei->elapsed_ns);
> +		drm_printf(p, "drm-cycles-%s:\t%llu\n",
> +			   ei->name, ei->cycles);
> +		drm_printf(p, "drm-maxfreq-%s:\t%lu Hz\n",
> +			   ei->name, panfrost_priv->fdinfo.maxfreq);
> +		drm_printf(p, "drm-curfreq-%s:\t%lu Hz\n",
> +			   ei->name, pfdev->pfdevfreq.current_frequency);
> +	}
> +}
> +
> +static void panfrost_show_fdinfo(struct drm_printer *p, struct drm_file *file)
> +{
> +	struct drm_device *dev = file->minor->dev;
> +	struct panfrost_device *pfdev = dev->dev_private;
> +
> +	panfrost_gpu_show_fdinfo(pfdev, file->driver_priv, p);
> +
> +}
> +
> +static const struct file_operations panfrost_drm_driver_fops = {
> +	.owner = THIS_MODULE,
> +	DRM_GEM_FOPS,
> +	.show_fdinfo = drm_show_fdinfo,
> +};
>  
>  /*
>   * Panfrost driver version:
> @@ -536,6 +592,7 @@ static const struct drm_driver panfrost_drm_driver = {
>  	.driver_features	= DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ,
>  	.open			= panfrost_open,
>  	.postclose		= panfrost_postclose,
> +	.show_fdinfo		= panfrost_show_fdinfo,
>  	.ioctls			= panfrost_drm_driver_ioctls,
>  	.num_ioctls		= ARRAY_SIZE(panfrost_drm_driver_ioctls),
>  	.fops			= &panfrost_drm_driver_fops,
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index 8b1bf6ac48f8..8a02e1ee9f9b 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -159,6 +159,25 @@ panfrost_dequeue_job(struct panfrost_device *pfdev, int slot)
>  	struct panfrost_job *job = pfdev->jobs[slot][0];
>  
>  	WARN_ON(!job);
> +	if (job->priv) {
> +		struct engine_info *engine_info = &job->priv->fdinfo.engines[slot];
> +
> +		if (atomic_read(&pfdev->profile_mode)) {
> +			engine_info->elapsed_ns +=
> +				ktime_to_ns(ktime_sub(ktime_get(), job->start_time));
> +			engine_info->cycles +=
> +				panfrost_cycle_counter_read(pfdev) - job->start_cycles;
> +
> +			/* Reset in case the job has to be requeued */
> +			job->start_time = 0;
> +			/* A GPU reset puts the Cycle Counter register back to 0 */
> +			job->start_cycles = atomic_read(&pfdev->reset.pending) ?
> +				0 : panfrost_cycle_counter_read(pfdev);
> +		}
> +	} else
> +		dev_WARN(pfdev->dev, "Panfrost DRM file closed when job was on flight\n");
> +
> +
>  	pfdev->jobs[slot][0] = pfdev->jobs[slot][1];
>  	pfdev->jobs[slot][1] = NULL;
>  
> @@ -233,6 +252,11 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)
>  	subslot = panfrost_enqueue_job(pfdev, js, job);
>  	/* Don't queue the job if a reset is in progress */
>  	if (!atomic_read(&pfdev->reset.pending)) {
> +		if (atomic_read(&pfdev->profile_mode)) {
> +			job->start_time = ktime_get();
> +			job->start_cycles = panfrost_cycle_counter_read(pfdev);
> +		}
> +
>  		job_write(pfdev, JS_COMMAND_NEXT(js), JS_COMMAND_START);
>  		dev_dbg(pfdev->dev,
>  			"JS: Submitting atom %p to js[%d][%d] with head=0x%llx AS %d",
> @@ -936,6 +960,9 @@ void panfrost_job_close(struct panfrost_file_priv *panfrost_priv)
>  			}
>  
>  			job_write(pfdev, JS_COMMAND(i), cmd);
> +
> +			/* Jobs can outlive their file context */
> +			job->priv = NULL;
>  		}
>  	}
>  	spin_unlock(&pfdev->js->job_lock);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.h b/drivers/gpu/drm/panfrost/panfrost_job.h
> index 2aa0add35459..63bc830e057d 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.h
> @@ -32,7 +32,11 @@ struct panfrost_job {
>  
>  	/* Fence to be signaled by drm-sched once its done with the job */
>  	struct dma_fence *render_done_fence;
> +
> +	struct panfrost_file_priv *priv;
>  	bool is_profiled;
> +	ktime_t start_time;
> +	u64 start_cycles;
>  };
>  
>  int panfrost_job_init(struct panfrost_device *pfdev);