Tried to make pbvh bmesh normals calc a bit more efficient.

source/blender/blenkernel/intern/pbvh.c

@@ -52,6 +52,7 @@
 #include <limits.h>
 
 #define LEAF_LIMIT 4000
+#define LEAF_DEPTH_LIMIT 18
 
 //#define PERFCNTRS
 
@@ -485,13 +486,15 @@ static bool leaf_needs_material_split(PBVH *pbvh, int offset, int count)
  * offset and start indicate a range in the array of primitive indices
  */
 
-static void build_sub(PBVH *pbvh, int node_index, BB *cb, BBC *prim_bbc, int offset, int count)
+static void build_sub(
+    PBVH *pbvh, int node_index, BB *cb, BBC *prim_bbc, int offset, int count, int depth)
 {
   int end;
   BB cb_backing;
 
   /* Decide whether this is a leaf or not */
-  const bool below_leaf_limit = count <= pbvh->leaf_limit;
+  const bool below_leaf_limit = count <= pbvh->leaf_limit || depth >= pbvh->depth_limit;
+
   if (below_leaf_limit) {
     if (!leaf_needs_material_split(pbvh, offset, count)) {
       build_leaf(pbvh, node_index, prim_bbc, offset, count);
@@ -531,13 +534,20 @@ static void build_sub(PBVH *pbvh, int node_index, BB *cb, BBC *prim_bbc, int off
   }
 
   /* Build children */
-  build_sub(pbvh, pbvh->nodes[node_index].children_offset, NULL, prim_bbc, offset, end - offset);
+  build_sub(pbvh,
+            pbvh->nodes[node_index].children_offset,
+            NULL,
+            prim_bbc,
+            offset,
+            end - offset,
+            depth + 1);
   build_sub(pbvh,
             pbvh->nodes[node_index].children_offset + 1,
             NULL,
             prim_bbc,
             end,
-            offset + count - end);
+            offset + count - end,
+            depth + 1);
 }
 
 static void pbvh_build(PBVH *pbvh, BB *cb, BBC *prim_bbc, int totprim)
@@ -562,7 +572,7 @@ static void pbvh_build(PBVH *pbvh, BB *cb, BBC *prim_bbc, int totprim)
   }
 
   pbvh->totnode = 1;
-  build_sub(pbvh, 0, cb, prim_bbc, 0, totprim);
+  build_sub(pbvh, 0, cb, prim_bbc, 0, totprim, 0);
 }
 
 /**
@@ -595,6 +605,8 @@ void BKE_pbvh_build_mesh(PBVH *pbvh,
   pbvh->vert_bitmap = BLI_BITMAP_NEW(totvert, "bvh->vert_bitmap");
   pbvh->totvert = totvert;
   pbvh->leaf_limit = LEAF_LIMIT;
+  pbvh->depth_limit = LEAF_DEPTH_LIMIT;
+
   pbvh->vdata = vdata;
   pbvh->ldata = ldata;
   pbvh->pdata = pdata;

source/blender/blenkernel/intern/pbvh_bmesh.c

@@ -3263,7 +3263,36 @@ static void pbvh_update_normals_task_cb(void *__restrict userdata,
   TGSET_ITER_END
 
   TGSET_ITER (v, node->bm_unique_verts) {
-    BM_vert_normal_update(v);
+    // BM_vert_normal_update(v);
+    // optimized loop
+    BMEdge *e = v->e;
+
+    zero_v3(v->no);
+
+    if (!e) {
+      continue;
+    }
+
+    do {
+      BMLoop *l = e->l;
+
+      if (!l) {
+        e = v == e->v1 ? e->v1_disk_link.next : e->v2_disk_link.next;
+        continue;
+      }
+
+      do {
+        v->no[0] += l->f->no[0];
+        v->no[1] += l->f->no[1];
+        v->no[2] += l->f->no[2];
+
+        l = l->radial_next;
+      } while (l != e->l);
+
+      e = v == e->v1 ? e->v1_disk_link.next : e->v2_disk_link.next;
+    } while (e != v->e);
+
+    normalize_v3(v->no);
   }
   TGSET_ITER_END
 
@@ -3557,6 +3586,8 @@ void BKE_pbvh_build_bmesh(PBVH *pbvh,
   pbvh->cd_vcol_offset = CustomData_get_offset(&bm->vdata, CD_PROP_COLOR);
   pbvh->cd_faceset_offset = CustomData_get_offset(&bm->pdata, CD_SCULPT_FACE_SETS);
 
+  pbvh->depth_limit = 18;
+
   /* TODO: choose leaf limit better */
   pbvh->leaf_limit = 1000;
 

source/blender/blenkernel/intern/pbvh_intern.h

@@ -138,6 +138,7 @@ struct PBVH {
   int totvert;
 
   int leaf_limit;
+  int depth_limit;
 
   /* Mesh data */
   const struct Mesh *mesh;

source/blender/editors/sculpt_paint/sculpt_dyntopo.c

@@ -92,8 +92,12 @@ void SCULPT_reorder_bmesh(SculptSession *ss)
   SCULPT_face_random_access_ensure(ss);
   SCULPT_vertex_random_access_ensure(ss);
 
-  int actv = ss->active_vertex_index.i ? BKE_pbvh_vertex_index_to_table(ss->pbvh, ss->active_vertex_index) : -1;
-  int actf =ss->active_face_index.i ? BKE_pbvh_face_index_to_table(ss->pbvh, ss->active_face_index) : -1;
+  int actv = ss->active_vertex_index.i ?
+                 BKE_pbvh_vertex_index_to_table(ss->pbvh, ss->active_vertex_index) :
+                 -1;
+  int actf = ss->active_face_index.i ?
+                 BKE_pbvh_face_index_to_table(ss->pbvh, ss->active_face_index) :
+                 -1;
 
   if (ss->bm_log) {
     BM_log_full_mesh(ss->bm, ss->bm_log);
@@ -110,7 +114,7 @@ void SCULPT_reorder_bmesh(SculptSession *ss)
   if (actf >= 0) {
     ss->active_face_index = BKE_pbvh_table_index_to_face(ss->pbvh, actf);
   }
-  
+
   SCULPT_dyntopo_node_layers_update_offsets(ss);
 
   if (ss->bm_log) {