Re: [PATCH v2] drm/v3d: Add DRM_IOCTL_V3D_PERFMON_SET_GLOBAL

["Maíra Canal" <mcanal@igalia.com>]

Hi Christian,

Thanks for your patch! Just some small nits.

On 31/10/24 17:51, Christian Gmeiner wrote:
> From: Christian Gmeiner <cgmeiner@igalia.com>
> 
> Add a new ioctl, DRM_IOCTL_V3D_PERFMON_SET_GLOBAL, to allow
> configuration of a global performance monitor (perfmon).
> Use the global perfmon for all jobs to ensure consistent
> performance tracking across submissions.

I'd mention how this feature can be useful for user-space (for example,
the implementation of a Perfetto datasource).

> 
> Signed-off-by: Christian Gmeiner <cgmeiner@igalia.com>
> 
> ---
> Changes in v2:
> - Reworked commit message.
> - Removed num_perfmon counter for tracking perfmon allocations.
> - Allowing allocation of perfmons when the global perfmon is active.
> - Return -EAGAIN for submissions with a per job perfmon if the global perfmon is active.
> ---
>   drivers/gpu/drm/v3d/v3d_drv.c     |  1 +
>   drivers/gpu/drm/v3d/v3d_drv.h     |  8 ++++++++
>   drivers/gpu/drm/v3d/v3d_perfmon.c | 34 +++++++++++++++++++++++++++++++
>   drivers/gpu/drm/v3d/v3d_sched.c   | 14 ++++++++++---
>   drivers/gpu/drm/v3d/v3d_submit.c  | 10 +++++++++
>   include/uapi/drm/v3d_drm.h        | 15 ++++++++++++++
>   6 files changed, 79 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/v3d/v3d_drv.c b/drivers/gpu/drm/v3d/v3d_drv.c
> index d7ff1f5fa481..3c89f0daa5b8 100644
> --- a/drivers/gpu/drm/v3d/v3d_drv.c
> +++ b/drivers/gpu/drm/v3d/v3d_drv.c
> @@ -214,6 +214,7 @@ static const struct drm_ioctl_desc v3d_drm_ioctls[] = {
>   	DRM_IOCTL_DEF_DRV(V3D_PERFMON_GET_VALUES, v3d_perfmon_get_values_ioctl, DRM_RENDER_ALLOW),
>   	DRM_IOCTL_DEF_DRV(V3D_SUBMIT_CPU, v3d_submit_cpu_ioctl, DRM_RENDER_ALLOW | DRM_AUTH),
>   	DRM_IOCTL_DEF_DRV(V3D_PERFMON_GET_COUNTER, v3d_perfmon_get_counter_ioctl, DRM_RENDER_ALLOW),
> +	DRM_IOCTL_DEF_DRV(V3D_PERFMON_SET_GLOBAL, v3d_perfmon_set_global_ioctl, DRM_RENDER_ALLOW),
>   };
>   
>   static const struct drm_driver v3d_drm_driver = {
> diff --git a/drivers/gpu/drm/v3d/v3d_drv.h b/drivers/gpu/drm/v3d/v3d_drv.h
> index cf4b23369dc4..a0d920ec2b1d 100644
> --- a/drivers/gpu/drm/v3d/v3d_drv.h
> +++ b/drivers/gpu/drm/v3d/v3d_drv.h
> @@ -179,6 +179,12 @@ struct v3d_dev {
>   		u32 num_allocated;
>   		u32 pages_allocated;
>   	} bo_stats;
> +
> +	/* To support a performance analysis tool in user space, we require
> +	 * a single, globally configured performance monitor (perfmon) for
> +	 * all jobs.
> +	 */
> +	struct v3d_perfmon *global_perfmon;
>   };
>   
>   static inline struct v3d_dev *
> @@ -584,6 +590,8 @@ int v3d_perfmon_get_values_ioctl(struct drm_device *dev, void *data,
>   				 struct drm_file *file_priv);
>   int v3d_perfmon_get_counter_ioctl(struct drm_device *dev, void *data,
>   				  struct drm_file *file_priv);
> +int v3d_perfmon_set_global_ioctl(struct drm_device *dev, void *data,
> +				 struct drm_file *file_priv);
>   
>   /* v3d_sysfs.c */
>   int v3d_sysfs_init(struct device *dev);
> diff --git a/drivers/gpu/drm/v3d/v3d_perfmon.c b/drivers/gpu/drm/v3d/v3d_perfmon.c
> index 156be13ab2ef..bf42303c292b 100644
> --- a/drivers/gpu/drm/v3d/v3d_perfmon.c
> +++ b/drivers/gpu/drm/v3d/v3d_perfmon.c
> @@ -312,6 +312,9 @@ static int v3d_perfmon_idr_del(int id, void *elem, void *data)
>   	if (perfmon == v3d->active_perfmon)
>   		v3d_perfmon_stop(v3d, perfmon, false);
>   
> +	/* If the global perfmon is being destroyed, set it to NULL */
> +	cmpxchg(&v3d->global_perfmon, perfmon, NULL);
> +
>   	v3d_perfmon_put(perfmon);
>   
>   	return 0;
> @@ -451,3 +454,34 @@ int v3d_perfmon_get_counter_ioctl(struct drm_device *dev, void *data,
>   
>   	return 0;
>   }

[...]

> index 87fc5bb0a61e..709724fe28e6 100644
> --- a/include/uapi/drm/v3d_drm.h
> +++ b/include/uapi/drm/v3d_drm.h
> @@ -43,6 +43,7 @@ extern "C" {
>   #define DRM_V3D_PERFMON_GET_VALUES                0x0a
>   #define DRM_V3D_SUBMIT_CPU                        0x0b
>   #define DRM_V3D_PERFMON_GET_COUNTER               0x0c
> +#define DRM_V3D_PERFMON_SET_GLOBAL                0x0d
>   
>   #define DRM_IOCTL_V3D_SUBMIT_CL           DRM_IOWR(DRM_COMMAND_BASE + DRM_V3D_SUBMIT_CL, struct drm_v3d_submit_cl)
>   #define DRM_IOCTL_V3D_WAIT_BO             DRM_IOWR(DRM_COMMAND_BASE + DRM_V3D_WAIT_BO, struct drm_v3d_wait_bo)
> @@ -61,6 +62,8 @@ extern "C" {
>   #define DRM_IOCTL_V3D_SUBMIT_CPU          DRM_IOW(DRM_COMMAND_BASE + DRM_V3D_SUBMIT_CPU, struct drm_v3d_submit_cpu)
>   #define DRM_IOCTL_V3D_PERFMON_GET_COUNTER DRM_IOWR(DRM_COMMAND_BASE + DRM_V3D_PERFMON_GET_COUNTER, \
>   						   struct drm_v3d_perfmon_get_counter)
> +#define DRM_IOCTL_V3D_PERFMON_SET_GLOBAL  DRM_IOW(DRM_COMMAND_BASE + DRM_V3D_PERFMON_SET_GLOBAL, \
> +						   struct drm_v3d_perfmon_set_global)
>   
>   #define DRM_V3D_SUBMIT_CL_FLUSH_CACHE             0x01
>   #define DRM_V3D_SUBMIT_EXTENSION		  0x02
> @@ -765,6 +768,18 @@ struct drm_v3d_perfmon_get_counter {
>   	__u8 reserved[7];
>   };
>   
> +#define DRM_V3D_PERFMON_CLEAR_GLOBAL    0x0001
> +
> +/*

Please, use kernel-doc [1]. So, here is /**

[1] https://docs.kernel.org/doc-guide/kernel-doc.html

> + * struct drm_v3d_perfmon_set_global - ioctl to define a

The colunm width is 80.

> + * global performance counter that is used if a job has

s/counter/monitor

> + * not assigned one on its own.

This description isn't really precise. When the global performance
monitor is enabled, the job perfmon doesn't matter. Currently, we don't
even allow a job perfmon to be submitted, but if we did, the global
perfmon would be used even if the job had a perfmon.

Best Regards,
- Maíra

> + */
> +struct drm_v3d_perfmon_set_global {
> +	__u32 flags;
> +	__u32 id;
> +};
> +
>   #if defined(__cplusplus)
>   }
>   #endif