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authorEric Anholt <eric@anholt.net>2017-11-28 16:17:16 -0800
committerEric Anholt <eric@anholt.net>2017-12-01 15:37:28 -0800
commit0ed952c7e9b811bc11dec64bd4bebcdf4222cc85 (patch)
tree3f559f6dd6705c0724f3494736fbeebf1d7d96f5 /src/gallium/drivers/vc4
parent230e646a4013ed5d9c80c54d48ef0ac9ee4edbb0 (diff)
broadcom/vc4: Use a single-entry cached last_hindex value.
Since almost all BOs will be in one CL at a time, this cache will almost always hit except for the first usage of the BO in each CL. This didn't show up as statistically significant on the minetest trace (n=340), but if I lop off the throttled lobe of the bimodal distribution, it very clearly does (0.74731% +/- 0.162093%, n=269).
Diffstat (limited to 'src/gallium/drivers/vc4')
-rw-r--r--src/gallium/drivers/vc4/vc4_bufmgr.h8
-rw-r--r--src/gallium/drivers/vc4/vc4_cl.c14
2 files changed, 20 insertions, 2 deletions
diff --git a/src/gallium/drivers/vc4/vc4_bufmgr.h b/src/gallium/drivers/vc4/vc4_bufmgr.h
index 4e7b23e0862..e0f6bbcfd8b 100644
--- a/src/gallium/drivers/vc4/vc4_bufmgr.h
+++ b/src/gallium/drivers/vc4/vc4_bufmgr.h
@@ -39,6 +39,14 @@ struct vc4_bo {
uint32_t handle;
uint32_t size;
+ /* This will be read/written by multiple threads without a lock -- you
+ * should take a snapshot and use it to see if you happen to be in the
+ * CL's handles at this position, to make most lookups O(1). It's
+ * volatile to make sure that the compiler doesn't emit multiple loads
+ * from the address, which would make the lookup racy.
+ */
+ volatile uint32_t last_hindex;
+
/** Entry in the linked list of buffers freed, by age. */
struct list_head time_list;
/** Entry in the per-page-count linked list of buffers freed (by age). */
diff --git a/src/gallium/drivers/vc4/vc4_cl.c b/src/gallium/drivers/vc4/vc4_cl.c
index 508281a27bb..7ae092ebce3 100644
--- a/src/gallium/drivers/vc4/vc4_cl.c
+++ b/src/gallium/drivers/vc4/vc4_cl.c
@@ -61,10 +61,19 @@ vc4_gem_hindex(struct vc4_job *job, struct vc4_bo *bo)
{
uint32_t hindex;
uint32_t *current_handles = job->bo_handles.base;
+ uint32_t cl_hindex_count = cl_offset(&job->bo_handles) / 4;
+ uint32_t last_hindex = bo->last_hindex; /* volatile read! */
- for (hindex = 0; hindex < cl_offset(&job->bo_handles) / 4; hindex++) {
- if (current_handles[hindex] == bo->handle)
+ if (last_hindex < cl_hindex_count &&
+ current_handles[last_hindex] == bo->handle) {
+ return last_hindex;
+ }
+
+ for (hindex = 0; hindex < cl_hindex_count; hindex++) {
+ if (current_handles[hindex] == bo->handle) {
+ bo->last_hindex = hindex;
return hindex;
+ }
}
struct vc4_cl_out *out;
@@ -79,5 +88,6 @@ vc4_gem_hindex(struct vc4_job *job, struct vc4_bo *bo)
job->bo_space += bo->size;
+ bo->last_hindex = hindex;
return hindex;
}