[Mesa-dev] [PATCH 06/10] i965: Ignore reloc read/write domains

[Chris Wilson]

Since before the kernel supported I915_EXEC_NO_RELOC, long before our
minimum kernel requirement, the kernel unconditionally invalidated all
GPU TLBs before a batch and flushed all GPU caches after a batch. At
that moment, the only use for read/write domain was for activity
tracking, ensuring that future reads waited for the last writer and
future writes waited for all reads. This only requires a single bit in
the execbuf interface which can be supplied via the NO_RELOC interface,
making the use of relocation domains entirely redundant.

Trimming the excess writes into the array allows the compiler to be much
more frugal:

   text	   data	    bss	    dec	    hex	filename
8493790	 357184	 424944	9275918	 8d8a0e	i965_dri.baseline
8493758	 357184	 424944	9275886	 8d89ee	i965_dri.so

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Kenneth Graunke <kenneth at whitecape.org>
Cc: Matt Turner <mattst88 at gmail.com>
Cc: Jason Ekstrand <jason.ekstrand at intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 src/mesa/drivers/dri/i965/intel_batchbuffer.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
index fcdd95ed78..6009679c07 100644
--- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
+++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
@@ -798,17 +798,13 @@ brw_emit_reloc(struct intel_batchbuffer *batch, uint32_t batch_offset,
       offset64 = target->offset64;
    }
 
-   struct drm_i915_gem_relocation_entry *reloc =
-      &batch->relocs[batch->reloc_count];
-
-   batch->reloc_count++;
-
-   reloc->offset = batch_offset;
-   reloc->delta = target_offset;
-   reloc->target_handle = target->gem_handle;
-   reloc->read_domains = read_domains;
-   reloc->write_domain = write_domain;
-   reloc->presumed_offset = offset64;
+   batch->relocs[batch->reloc_count++] =
+      (struct drm_i915_gem_relocation_entry) {
+         .offset = batch_offset,
+         .delta = target_offset,
+         .target_handle = target->gem_handle,
+         .presumed_offset = offset64,
+      };
 
    /* Using the old buffer offset, write in what the right data would be, in
     * case the buffer doesn't move and we can short-circuit the relocation
-- 
2.13.3