util/sparse_array: Stash the node level in the node pointer
This reworks the data structure a bit and, in my view, simplifies it.
Instead of each node having a header which has the node level in it, we
use the bottom 6 bits of the pointer for that. This requires us to
allocate with the os_malloc/free_aligned helpers (which call into
posix_memalign on Linux) but cache-line aligning our allocations is
actually probably a good thing given that we're doing atomics on them.
The primary advantages to doing this is that it changes the number of
memory accesses per tree level from 2 to 1 when walking the tree because
we no longer have to look at node->level.
Reviewed-by: Lionel Landwerlin <[email protected]>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4228>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4228>
diff --git a/src/util/sparse_array.h b/src/util/sparse_array.h
index 3947a2f..f91fe21 100644
--- a/src/util/sparse_array.h
+++ b/src/util/sparse_array.h
@@ -69,7 +69,7 @@
size_t elem_size;
unsigned node_size_log2;
- struct util_sparse_array_node *root;
+ uintptr_t root;
};
void util_sparse_array_init(struct util_sparse_array *arr,
