[Intel-gfx] [PATCH 10/11] drm/i915/perf: limit OA buffer size to minimum when unread

[Lionel Landwerlin]

On 26/03/18 10:08, Lionel Landwerlin wrote:
> The way our hardware is designed doesn't seem to let us use the
> MI_RECORD_PERF_COUNT command without setting up a circular buffer.
>
> In the case where the user didn't request OA reports to be available
> through the i915 perf stream, we can set the OA buffer to the minimum
> size to avoid consuming memory which won't be used by the driver.
>
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_perf.c | 15 ++++++++++-----
>   1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 55c7631ad3c2..f8ec09e2d599 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -1372,7 +1372,8 @@ static void gen7_init_oa_buffer(struct drm_i915_private *dev_priv)
>   	 * the assumption that new reports are being written to zeroed
>   	 * memory...
>   	 */
There is an issue in both function programming the OA buffer. They still 
program the length of the buffer to 16Mb.
I'll send a v2.
> -	memset(dev_priv->perf.oa.oa_buffer.vaddr, 0, OA_BUFFER_SIZE);
> +	memset(dev_priv->perf.oa.oa_buffer.vaddr, 0,
> +	       dev_priv->perf.oa.oa_buffer.vma->size);
>   
>   	/* Maybe make ->pollin per-stream state if we support multiple
>   	 * concurrent streams in the future.
> @@ -1430,7 +1431,8 @@ static void gen8_init_oa_buffer(struct drm_i915_private *dev_priv)
>   	 * the assumption that new reports are being written to zeroed
>   	 * memory...
>   	 */
> -	memset(dev_priv->perf.oa.oa_buffer.vaddr, 0, OA_BUFFER_SIZE);
> +	memset(dev_priv->perf.oa.oa_buffer.vaddr, 0,
> +	       dev_priv->perf.oa.oa_buffer.vma->size);
>   
>   	/*
>   	 * Maybe make ->pollin per-stream state if we support multiple
> @@ -1439,10 +1441,13 @@ static void gen8_init_oa_buffer(struct drm_i915_private *dev_priv)
>   	dev_priv->perf.oa.pollin = false;
>   }
>   
> -static int alloc_oa_buffer(struct drm_i915_private *dev_priv)
> +static int alloc_oa_buffer(struct drm_i915_private *dev_priv,
> +			   struct i915_perf_stream *stream)
>   {
>   	struct drm_i915_gem_object *bo;
>   	struct i915_vma *vma;
> +	u32 buffer_size = (stream->sample_flags & SAMPLE_OA_REPORT) == 0 ?
> +		SZ_128K : OA_BUFFER_SIZE;
>   	int ret;
>   
>   	ret = i915_mutex_lock_interruptible(&dev_priv->drm);
> @@ -1457,7 +1462,7 @@ static int alloc_oa_buffer(struct drm_i915_private *dev_priv)
>   	BUILD_BUG_ON_NOT_POWER_OF_2(OA_BUFFER_SIZE);
>   	BUILD_BUG_ON(OA_BUFFER_SIZE < SZ_128K || OA_BUFFER_SIZE > SZ_16M);
>   
> -	bo = i915_gem_object_create(dev_priv, OA_BUFFER_SIZE);
> +	bo = i915_gem_object_create(dev_priv, buffer_size);
>   	if (IS_ERR(bo)) {
>   		DRM_ERROR("Failed to allocate OA buffer\n");
>   		ret = PTR_ERR(bo);
> @@ -2148,7 +2153,7 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream,
>   	intel_runtime_pm_get(dev_priv);
>   	intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
>   
> -	ret = alloc_oa_buffer(dev_priv);
> +	ret = alloc_oa_buffer(dev_priv, stream);
>   	if (ret)
>   		goto err_oa_buf_alloc;
>