Mesa (master): freedreno: Avoid duplicate BO relocs in FD_RINGBUFFER_OBJECTs.

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Module: Mesa
Branch: master
Commit: b1151cd2ffc821a09130f87c2a266b2bfe7b0822
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b1151cd2ffc821a09130f87c2a266b2bfe7b0822

Author: Eric Anholt <eric at anholt.net>
Date:   Fri May  8 14:53:47 2020 -0700

freedreno: Avoid duplicate BO relocs in FD_RINGBUFFER_OBJECTs.

For the piglit drawoverhead case, 5/18 of the objects' relocs were
duplicated.  We can dedupe them at object create time (since objects are
long-lived) and avoid repeated relocation work at emit time.

nohw drawoverhead program statechange throughput 2.34082% +/- 0.645832%
(n=10).

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5020>

---

 src/freedreno/drm/msm_ringbuffer_sp.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/freedreno/drm/msm_ringbuffer_sp.c b/src/freedreno/drm/msm_ringbuffer_sp.c
index 6bab90b190a..869c41ddda6 100644
--- a/src/freedreno/drm/msm_ringbuffer_sp.c
+++ b/src/freedreno/drm/msm_ringbuffer_sp.c
@@ -385,9 +385,23 @@ msm_ringbuffer_sp_emit_reloc(struct fd_ringbuffer *ring,
 	struct fd_pipe *pipe;
 
 	if (ring->flags & _FD_RINGBUFFER_OBJECT) {
-		unsigned idx = APPEND(&msm_ring->u, reloc_bos);
-
-		msm_ring->u.reloc_bos[idx] = fd_bo_ref(reloc->bo);
+		/* Avoid emitting duplicate BO references into the list.  Ringbuffer
+		 * objects are long-lived, so this saves ongoing work at draw time in
+		 * exchange for a bit at context setup/first draw.  And the number of
+		 * relocs per ringbuffer object is fairly small, so the O(n^2) doesn't
+		 * hurt much.
+		 */
+		bool found = false;
+		for (int i = 0; i < msm_ring->u.nr_reloc_bos; i++) {
+			if (msm_ring->u.reloc_bos[i] == reloc->bo) {
+				found = true;
+				break;
+			}
+		}
+		if (!found) {
+			unsigned idx = APPEND(&msm_ring->u, reloc_bos);
+			msm_ring->u.reloc_bos[idx] = fd_bo_ref(reloc->bo);
+		}
 
 		pipe = msm_ring->u.pipe;
 	} else {