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

Boris Brezillon
2023-09-06T07:44:10Z

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);