Commit 0ed952c7 authored by Eric Anholt's avatar Eric Anholt

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).
parent 230e646a
......@@ -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). */
......@@ -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;
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