[Feature] Further optimization to the hot path

We check userdata very frequently, so the idea here is the following:

- Store the address of classname (converted to int) in the metatable at index 1
- When we need to check some udata, we can just compare the static address with
  the integer stored in metatable
- This avoid quite an expensive `lua_rawequal` call for two tables as we know that
  our classes are quite static

diff --git a/src/lua/lua_common.c b/src/lua/lua_common.c
index 8474ff79050f0b87661c1bf05a2210275057a407..92e26417af660ec75cea98f36232fd89fbcefd94 100644 (file)
--- a/src/lua/lua_common.c
+++ b/src/lua/lua_common.c
@@ -122,6 +122,9 @@ void rspamd_lua_new_class(lua_State *L,
        int offset = luaL_ref(L, LUA_REGISTRYINDEX);
        k = kh_put(lua_class_set, ctx->classes, GPOINTER_TO_INT(classname), &r);
        kh_value(ctx->classes, k) = offset;
+       /* Set class name as a metatable[1] converted to an integer for faster comparisons */
+       lua_pushinteger(L, GPOINTER_TO_INT(classname));
+       lua_rawseti(L, -2, 1);
        /* MT is left on stack ! */
 }
 
@@ -1980,17 +1983,18 @@ rspamd_lua_check_udata_common(lua_State *L, gint pos, const gchar *classname,
        else {
                /* Match class */
                if (lua_getmetatable(L, pos)) {
-                       struct rspamd_lua_context *ctx = rspamd_lua_ctx_by_state(L);
+                       /* Get mt[1] and check if it is an iteger */
+                       lua_rawgeti(L, -1, 1);
 
-                       k = kh_get(lua_class_set, ctx->classes, GPOINTER_TO_INT(classname));
-
-                       if (k == kh_end(ctx->classes)) {
+                       if (!lua_isnumber(L, -1)) {
+                               lua_pop(L, 1);
                                goto err;
                        }
 
-                       lua_rawgeti(L, LUA_REGISTRYINDEX, kh_value(ctx->classes, k));
+                       lua_Integer idx = lua_tointeger(L, -1);
+                       lua_pop(L, 1);
 
-                       if (!lua_rawequal(L, -1, -2)) {
+                       if (idx != GPOINTER_TO_INT(classname)) {
                                goto err;
                        }
                }