Re: [PATCH v3 07/10] drm/msm/A6xx: Add traces for preemption

[Akhil P Oommen]

On Thu, Sep 05, 2024 at 04:51:25PM +0200, Antonino Maniscalco wrote:
> Add trace points corresponding to preemption being triggered and being
> completed for latency measurement purposes.
> 
> Signed-off-by: Antonino Maniscalco <antomani103@xxxxxxxxx>
> Tested-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx> # on SM8650-QRD
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_preempt.c |  7 +++++++
>  drivers/gpu/drm/msm/msm_gpu_trace.h       | 28 ++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> index ec44f44d925f..ca9d36c107f2 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> @@ -7,6 +7,7 @@
>  #include "a6xx_gpu.h"
>  #include "a6xx_gmu.xml.h"
>  #include "msm_mmu.h"
> +#include "msm_gpu_trace.h"
>  
>  /*
>   * Try to transition the preemption state from old to new. Return
> @@ -143,6 +144,8 @@ void a6xx_preempt_irq(struct msm_gpu *gpu)
>  
>  	set_preempt_state(a6xx_gpu, PREEMPT_NONE);
>  
> +	trace_msm_gpu_preemption_irq(a6xx_gpu->cur_ring->id);
> +
>  	/*
>  	 * Retrigger preemption to avoid a deadlock that might occur when preemption
>  	 * is skipped due to it being already in flight when requested.
> @@ -264,6 +267,10 @@ void a6xx_preempt_trigger(struct msm_gpu *gpu)
>  	 */
>  	ring->skip_inline_wptr = false;
>  
> +	trace_msm_gpu_preemption_trigger(
> +		a6xx_gpu->cur_ring ? a6xx_gpu->cur_ring->id : -1,

Can't we avoid this check?

-Akhil.

> +		ring ? ring->id : -1);
> +
>  	spin_unlock_irqrestore(&ring->preempt_lock, flags);
>  
>  	gpu_write64(gpu,
> diff --git a/drivers/gpu/drm/msm/msm_gpu_trace.h b/drivers/gpu/drm/msm/msm_gpu_trace.h
> index ac40d857bc45..7f863282db0d 100644
> --- a/drivers/gpu/drm/msm/msm_gpu_trace.h
> +++ b/drivers/gpu/drm/msm/msm_gpu_trace.h
> @@ -177,6 +177,34 @@ TRACE_EVENT(msm_gpu_resume,
>  		TP_printk("%u", __entry->dummy)
>  );
>  
> +TRACE_EVENT(msm_gpu_preemption_trigger,
> +		TP_PROTO(int ring_id_from, int ring_id_to),
> +		TP_ARGS(ring_id_from, ring_id_to),
> +		TP_STRUCT__entry(
> +			__field(int, ring_id_from)
> +			__field(int, ring_id_to)
> +			),
> +		TP_fast_assign(
> +			__entry->ring_id_from = ring_id_from;
> +			__entry->ring_id_to = ring_id_to;
> +			),
> +		TP_printk("preempting %u -> %u",
> +			  __entry->ring_id_from,
> +			  __entry->ring_id_to)
> +);
> +
> +TRACE_EVENT(msm_gpu_preemption_irq,
> +		TP_PROTO(u32 ring_id),
> +		TP_ARGS(ring_id),
> +		TP_STRUCT__entry(
> +			__field(u32, ring_id)
> +			),
> +		TP_fast_assign(
> +			__entry->ring_id = ring_id;
> +			),
> +		TP_printk("preempted to %u", __entry->ring_id)
> +);
> +
>  #endif
>  
>  #undef TRACE_INCLUDE_PATH
> 
> -- 
> 2.46.0
>