[Mesa-dev] [PATCH v4 3/5] i965/miptree: Use cpu tiling/detiling when mapping

[Scott D Phillips]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Quoting Scott D Phillips (2018-04-03 21:05:43)
>> Rename the (un)map_gtt functions to (un)map_map (map by
>> returning a map) and add new functions (un)map_tiled_memcpy that
>> return a shadow buffer populated with the intel_tiled_memcpy
>> functions.
>> 
>> Tiling/detiling with the cpu will be the only way to handle Yf/Ys
>> tiling, when support is added for those formats.
>> 
>> v2: Compute extents properly in the x|y-rounded-down case (Chris Wilson)
>> 
>> v3: Add units to parameter names of tile_extents (Nanley Chery)
>>     Use _mesa_align_malloc for the shadow copy (Nanley)
>>     Continue using gtt maps on gen4 (Nanley)
>> 
>> v4: Use streaming_load_memcpy when detiling
>> ---
>>  src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 108 ++++++++++++++++++++++++--
>>  1 file changed, 100 insertions(+), 8 deletions(-)
>> 
>> diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
>> index 23cb40f3226..58ffe868d0d 100644
>> --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
>> +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c

[...]

>> @@ -3093,11 +3094,93 @@ intel_miptree_map_gtt(struct brw_context *brw,
>>  }
>>  
>>  static void
>> -intel_miptree_unmap_gtt(struct intel_mipmap_tree *mt)
>> +intel_miptree_unmap_map(struct intel_mipmap_tree *mt)
>>  {
>>     intel_miptree_unmap_raw(mt);
>>  }
>>  
>> +/* Compute extent parameters for use with tiled_memcpy functions.
>> + * xs are in units of bytes and ys are in units of strides. */
>> +static inline void
>> +tile_extents(struct intel_mipmap_tree *mt, struct intel_miptree_map *map,
>> +             unsigned int level, unsigned int slice, unsigned int *x1_B,
>> +             unsigned int *x2_B, unsigned int *y1_el, unsigned int *y2_el)
>> +{
>> +   unsigned int block_width, block_height;
>> +   unsigned int x0_el, y0_el;
>> +
>> +   _mesa_get_format_block_size(mt->format, &block_width, &block_height);
>> +
>> +   assert(map->x % block_width == 0);
>> +   assert(map->y % block_height == 0);
>> +
>> +   intel_miptree_get_image_offset(mt, level, slice, &x0_el, &y0_el);
>> +   *x1_B = (map->x / block_width + x0_el) * mt->cpp;
>> +   *y1_el = map->y / block_height + y0_el;
>> +   *x2_B = (DIV_ROUND_UP(map->x + map->w, block_width) + x0_el) * mt->cpp;
>> +   *y2_el = DIV_ROUND_UP(map->y + map->h, block_height) + y0_el;
>> +}
>> +
>> +static void
>> +intel_miptree_map_tiled_memcpy(struct brw_context *brw,
>> +                               struct intel_mipmap_tree *mt,
>> +                               struct intel_miptree_map *map,
>> +                               unsigned int level, unsigned int slice)
>> +{
>> +   unsigned int x1, x2, y1, y2;
>> +   tile_extents(mt, map, level, slice, &x1, &x2, &y1, &y2);
>> +   map->stride = ALIGN(_mesa_format_row_stride(mt->format, map->w), 16);
>> +
>> +   /* The tiling and detiling functions require that the linear buffer
>> +    * has proper 16-byte alignment (that is, `x0` is 16-byte aligned).
>
> Throw in an its here, i.e.  (that is, its `x0`...) Just spent a few
> moments going what x0 before remembering it's the internal x0 of
> tiled_to_linear().
>
> We really want to move that knowledge back to intel_tiled_memcpy.c. A
> single user isn't enough to justify a lot of effort though (or be sure
> you get the interface right).

You mean putting the code to decide the stride and alignment
requirements by the detiling code, something like
alloc_linear_for_tiled?

>> +    * Here we over-allocate the linear buffer by enough bytes to get
>> +    * the proper alignment.
>> +    */
>> +   map->buffer = _mesa_align_malloc(map->stride * (y2 - y1) + (x1 & 0xf), 16);
>> +   map->ptr = (char *)map->buffer + (x1 & 0xf);
>> +   assert(map->buffer);
>> +
>> +   if (!(map->mode & GL_MAP_INVALIDATE_RANGE_BIT)) {
>> +      char *src = intel_miptree_map_raw(brw, mt, map->mode | MAP_RAW);
>> +      src += mt->offset;
>> +
>> +      const mem_copy_fn fn =
>> +#if defined(USE_SSE41)
>> +         cpu_has_sse4_1 ? (mem_copy_fn)_mesa_streaming_load_memcpy :
>> +#endif
>> +         memcpy;
>
> So always use a streaming load and bypass cache, even coming from WB.
> Justifiable I believe, since there is no reason to keep it in cache as
> the modification is on map->buffer not the tiled bo.
>
> But do we want to use this path if !USE_SSE41 and WC? Let's see if
> that's excluded.

Presently the logic is to always do map_tiled_memcpy for tiled surfaces,
except on gen 4 where we finally could do a gtt map. You're saying we're
better off doing a gtt map if we do have a wc map and don't have
movntdqa? That sounds reasonable

>>  static void
>>  intel_miptree_map_blit(struct brw_context *brw,
>>                        struct intel_mipmap_tree *mt,
>> @@ -3655,8 +3738,11 @@ intel_miptree_map(struct brw_context *brw,
>>                (mt->surf.row_pitch % 16 == 0)) {
>>        intel_miptree_map_movntdqa(brw, mt, map, level, slice);
>>  #endif
>> +   } else if (mt->surf.tiling != ISL_TILING_LINEAR &&
>> +              brw->screen->devinfo.gen > 4) {
>> +      intel_miptree_map_tiled_memcpy(brw, mt, map, level, slice);
>>     } else {
>> -      intel_miptree_map_gtt(brw, mt, map, level, slice);
>> +      intel_miptree_map_map(brw, mt, map, level, slice);
>
> Ah, the remaining choice is to go through a GTT map if tiled_memcpy
> doesn't support it.
>
> So memcpy is the only option right now, that is painful. Maybe use
> perf_debug if we hit map_map.
>
> I'm never sure how map_blit ties into this. We definitely want to use
> the direct copy over the indirect blit in the majority, if not all,
> cases.
>
> As it stands, as an improvement over map_gtt,
> From: Chris Wilson <chris at chris-wilson.co.uk>

Was this meant to be R-b, or maybe it's the pointed absence of one :)