Hi,
In my application, I need to read pixels back to system memory for every
rendered frame. My approach is to create a chain of textures with
PIPE_USAGE_STAGING flag, and copy the render target to the staging
textures before reading them to avoid pipeline stall.
Now I found out as in the patch below, there's a line of code checking
whether the texture volume has more than 1024 pixels and will use a
staging texture if so. However the texture I am mapping is already
staging and can be surely mapped directly regardless of its volume. This
checking does not make any sense for me and is causing significant
performance penalty. I have tried removing it and nothing is broken,
performance can go up 10-20% in my case.
Please point it out if I missed anything here, otherwise I suggest this
two lines of code should be removed.
Thanks in advanced.
Vic
diff --git a/src/gallium/drivers/r600/r600_texture.c
b/src/gallium/drivers/r600/r600_texture.c
index 6de3d6a..536f88f 100644
--- a/src/gallium/drivers/r600/r600_texture.c
+++ b/src/gallium/drivers/r600/r600_texture.c
@@ -622,9 +622,6 @@ struct pipe_transfer*
r600_texture_get_transfer(struct pipe_context *ctx,
use_staging_texture = TRUE;
}
- if ((usage & PIPE_TRANSFER_READ) && u_box_volume(box) > 1024)
- use_staging_texture = TRUE;
-
/* Use a staging texture for uploads if the underlying BO is
busy. */
if (!(usage & PIPE_TRANSFER_READ) &&
(rctx->ws->cs_is_buffer_referenced(rctx->cs,
rtex->resource.cs_buf, RADEON_USAGE_READWRITE) ||
Vic
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