[Mesa-dev] [PATCH 4/4] i965: Use unsynchronized maps for the program cache on LLC platforms.

[Kristian Høgsberg]

On Fri, Aug 29, 2014 at 11:10:50PM -0700, Kenneth Graunke wrote:
> There's no reason to stall on pwrite - the CPU always appends to the
> buffer and never modifies existing contents, and the GPU never writes
> it.  Further, the CPU always appends new data before submitting a batch
> that requires it.
> 
> This code predates the unsynchronized mapping feature, so we simply
> didn't have the option when it was written.
> 
> Ideally, we would do this for non-LLC platforms too, but unsynchronized
> mapping support only exists for LLC systems.
> 
> Saves repeated 0.001ms stalls on program upload.
> 
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/brw_state_cache.c | 34 +++++++++++++++++++++++------
>  1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_state_cache.c b/src/mesa/drivers/dri/i965/brw_state_cache.c
> index b9bb0fc..1d2d32f 100644
> --- a/src/mesa/drivers/dri/i965/brw_state_cache.c
> +++ b/src/mesa/drivers/dri/i965/brw_state_cache.c
> @@ -172,14 +172,23 @@ brw_cache_new_bo(struct brw_cache *cache, uint32_t new_size)
>     drm_intel_bo *new_bo;
>  
>     new_bo = drm_intel_bo_alloc(brw->bufmgr, "program cache", new_size, 64);
> +   if (brw->has_llc)
> +      drm_intel_gem_bo_map_unsynchronized(new_bo);
>  
>     /* Copy any existing data that needs to be saved. */
>     if (cache->next_offset != 0) {
> -      brw_bo_map(brw, cache->bo, false, "program cache");
> -      drm_intel_bo_subdata(new_bo, 0, cache->next_offset, cache->bo->virtual);
> -      drm_intel_bo_unmap(cache->bo);
> +      if (brw->has_llc) {
> +         memcpy(new_bo->virtual, cache->bo->virtual, cache->next_offset);

Move the drm_intel_gem_bo_map_unsynchronized() and drm_intel_bo_unmap()
calls into this block so they bracket the memcpy as for the subdata case
below?

Other than that,

Reviewed-by: Kristian Høgsberg <krh at bitplanet.net>

> +      } else {
> +         brw_bo_map(brw, cache->bo, false, "program cache");
> +         drm_intel_bo_subdata(new_bo, 0, cache->next_offset,
> +                              cache->bo->virtual);
> +         drm_intel_bo_unmap(cache->bo);
> +      }
>     }
>  
> +   if (brw->has_llc)
> +      drm_intel_bo_unmap(cache->bo);
>     drm_intel_bo_unreference(cache->bo);
>     cache->bo = new_bo;
>     cache->bo_used_by_gpu = false;
> @@ -222,9 +231,11 @@ brw_try_upload_using_copy(struct brw_cache *cache,
>  	    continue;
>  	 }
>  
> -	 brw_bo_map(brw, cache->bo, false, "program cache");
> +         if (!brw->has_llc)
> +            brw_bo_map(brw, cache->bo, false, "program cache");
>  	 ret = memcmp(cache->bo->virtual + item->offset, data, item->size);
> -	 drm_intel_bo_unmap(cache->bo);
> +         if (!brw->has_llc)
> +            drm_intel_bo_unmap(cache->bo);
>  	 if (ret)
>  	    continue;
>  
> @@ -257,7 +268,7 @@ brw_upload_item_data(struct brw_cache *cache,
>     /* If we would block on writing to an in-use program BO, just
>      * recreate it.
>      */
> -   if (cache->bo_used_by_gpu) {
> +   if (!brw->has_llc && cache->bo_used_by_gpu) {
>        perf_debug("Copying busy program cache buffer.\n");
>        brw_cache_new_bo(cache, cache->bo->size);
>     }
> @@ -280,6 +291,7 @@ brw_upload_cache(struct brw_cache *cache,
>  		 uint32_t *out_offset,
>  		 void *out_aux)
>  {
> +   struct brw_context *brw = cache->brw;
>     struct brw_cache_item *item = CALLOC_STRUCT(brw_cache_item);
>     GLuint hash;
>     void *tmp;
> @@ -320,7 +332,11 @@ brw_upload_cache(struct brw_cache *cache,
>     cache->n_items++;
>  
>     /* Copy data to the buffer */
> -   drm_intel_bo_subdata(cache->bo, item->offset, data_size, data);
> +   if (brw->has_llc) {
> +      memcpy((char *) cache->bo->virtual + item->offset, data, data_size);
> +   } else {
> +      drm_intel_bo_subdata(cache->bo, item->offset, data_size, data);
> +   }
>  
>     *out_offset = item->offset;
>     *(void **)out_aux = (void *)((char *)item->key + item->key_size);
> @@ -342,6 +358,8 @@ brw_init_caches(struct brw_context *brw)
>     cache->bo = drm_intel_bo_alloc(brw->bufmgr,
>  				  "program cache",
>  				  4096, 64);
> +   if (brw->has_llc)
> +      drm_intel_gem_bo_map_unsynchronized(cache->bo);
>  
>     cache->aux_compare[BRW_VS_PROG] = brw_vs_prog_data_compare;
>     cache->aux_compare[BRW_GS_PROG] = brw_gs_prog_data_compare;
> @@ -408,6 +426,8 @@ brw_destroy_cache(struct brw_context *brw, struct brw_cache *cache)
>  
>     DBG("%s\n", __FUNCTION__);
>  
> +   if (brw->has_llc)
> +      drm_intel_bo_unmap(cache->bo);
>     drm_intel_bo_unreference(cache->bo);
>     cache->bo = NULL;
>     brw_clear_cache(brw, cache);
> -- 
> 2.1.0
> 
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