Periodic Lua Gc after loading Lua script

deps/lua/src/lapi.c

@@ -960,7 +960,22 @@ LUA_API int lua_gc (lua_State *L, int what, int data) {
   return res;
 }
 
-
+LUA_API int lua_gc_step (lua_State *L, int steps) {
+  int res = 0;
+  global_State *g;
+  lua_lock(L);
+  g = G(L);
+  g->GCthreshold = 0;
+  while (steps--) {
+    luaC_step(L);
+    if (g->gcstate == GCSpause) {  /* end of cycle? */
+      res = 1;  /* signal it */
+      break;
+    }
+  }
+  lua_unlock(L);
+  return res; 
+}
 
 /*
 ** miscellaneous functions

deps/lua/src/lua.h

@@ -228,6 +228,7 @@ LUA_API int  (lua_status) (lua_State *L);
 #define LUA_GCSETSTEPMUL	7
 
 LUA_API int (lua_gc) (lua_State *L, int what, int data);
+LUA_API int (lua_gc_step) (lua_State *L, int steps);
 
 
 /*

src/debug.c

@@ -1016,7 +1016,7 @@ NULL
         addReply(c, shared.ok);
     } else if (!strcasecmp(c->argv[1]->ptr,"script") && c->argc == 3) {
         if (!strcasecmp(c->argv[2]->ptr,"list")) {
-            dictIterator *di = dictGetIterator(getLuaScripts());
+            dictIterator *di = dictGetIterator(evalScriptsDict());
             dictEntry *de;
             while ((de = dictNext(di)) != NULL) {
                 luaScript *script = dictGetVal(de);
@@ -1026,7 +1026,7 @@ NULL
             dictReleaseIterator(di);
         } else if (sdslen(c->argv[2]->ptr) == 40) {
             dictEntry *de;
-            if ((de = dictFind(getLuaScripts(), c->argv[2]->ptr)) == NULL) {
+            if ((de = dictFind(evalScriptsDict(), c->argv[2]->ptr)) == NULL) {
                 addReplyErrorObject(c, shared.noscripterr);
                 return;
             }

src/eval.c

@@ -736,6 +736,10 @@ unsigned long evalScriptsMemory(void) {
             listLength(lctx.lua_scripts_lru_list) * sizeof(listNode);
 }
 
+void evalScriptsGC(void) {
+    lua_gc_step(lctx.lua, 1);
+}
+
 /* ---------------------------------------------------------------------------
  * LDB: Redis Lua debugging facilities
  * ------------------------------------------------------------------------- */
@@ -1737,7 +1741,3 @@ void luaLdbLineHook(lua_State *lua, lua_Debug *ar) {
         rctx->start_time = getMonotonicUs();
     }
 }
-
-dict *getLuaScripts(void) {
-    return lctx.lua_scripts;
-}

src/function_lua.c

@@ -183,6 +183,12 @@ static void luaEngineFreeFunction(void *engine_ctx, void *compiled_function) {
     zfree(f_ctx);
 }
 
+static void luaEnglineGCStep(void *engine_ctx, int steps) {
+    luaEngineCtx *lua_engine_ctx = engine_ctx;
+    lua_State *lua = lua_engine_ctx->lua;
+    lua_gc_step(lua, steps);
+}
+
 static void luaRegisterFunctionArgsInitialize(registerFunctionArgs *register_f_args,
     sds name,
     sds desc,
@@ -480,6 +486,7 @@ int luaEngineInitEngine(void) {
         .get_function_memory_overhead = luaEngineFunctionMemoryOverhead,
         .get_engine_memory_overhead = luaEngineMemoryOverhead,
         .free_function = luaEngineFreeFunction,
+        .gc_step = luaEnglineGCStep,
     };
     return functionsRegisterEngine(LUA_ENGINE_NAME, lua_engine);
 }

src/functions.c

@@ -1106,3 +1106,14 @@ int functionsInit(void) {
 
     return C_OK;
 }
+
+void functionsGC(void) {
+    dictIterator *iter = dictGetIterator(engines);
+    dictEntry *entry = NULL;
+    while ((entry = dictNext(iter))) {
+        engineInfo *ei = dictGetVal(entry);
+        engine *engine = ei->engine;
+        engine->gc_step(engine->engine_ctx, 1);
+    }
+    dictReleaseIterator(iter);
+}

src/functions.h

@@ -67,6 +67,9 @@ typedef struct engine {
 
     /* free the given function */
     void (*free_function)(void *engine_ctx, void *compiled_function);
+
+    /* Perform the garbage collector */
+    void (*gc_step)(void *engine_ctx, int steps);
 } engine;
 
 /* Hold information about an engine.
@@ -116,5 +119,6 @@ int functionLibCreateFunction(sds name, void *function, functionLibInfo *li, sds
 
 int luaEngineInitEngine(void);
 int functionsInit(void);
+void functionsGC(void);
 
 #endif /* __FUNCTIONS_H_ */

src/script.h

@@ -74,7 +74,6 @@ extern scriptFlag scripts_flags_def[];
 
 void luaEnvInit(void);
 lua_State *createLuaState(void);
-dict *getLuaScripts(void);
 uint64_t scriptFlagsToCmdFlags(uint64_t cmd_flags, uint64_t script_flags);
 int scriptPrepareForRun(scriptRunCtx *r_ctx, client *engine_client, client *caller, const char *funcname, uint64_t script_flags, int ro);
 void scriptResetRun(scriptRunCtx *r_ctx);

src/script_lua.c

@@ -1650,23 +1650,6 @@ void luaCallFunction(scriptRunCtx* run_ctx, lua_State *lua, robj** keys, size_t
         err = lua_pcall(lua,2,1,-4);
     }
 
-    /* Call the Lua garbage collector from time to time to avoid a
-     * full cycle performed by Lua, which adds too latency.
-     *
-     * The call is performed every LUA_GC_CYCLE_PERIOD executed commands
-     * (and for LUA_GC_CYCLE_PERIOD collection steps) because calling it
-     * for every command uses too much CPU. */
-    #define LUA_GC_CYCLE_PERIOD 50
-    {
-        static long gc_count = 0;
-
-        gc_count++;
-        if (gc_count == LUA_GC_CYCLE_PERIOD) {
-            lua_gc(lua,LUA_GCSTEP,LUA_GC_CYCLE_PERIOD);
-            gc_count = 0;
-        }
-    }
-
     if (err) {
         /* Error object is a table of the following format:
          * {err='<error msg>', source='<source file>', line=<line>}

src/server.c

@@ -1389,6 +1389,11 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
     /* Handle background operations on Redis databases. */
     databasesCron();
 
+    run_with_period(100) {
+        evalScriptsGC();
+        functionsGC();
+    }
+
     /* Start a scheduled AOF rewrite if this was requested by the user while
      * a BGSAVE was in progress. */
     if (!hasActiveChildProcess() &&

src/server.h

@@ -3475,6 +3475,7 @@ void sha1hex(char *digest, char *script, size_t len);
 unsigned long evalMemory(void);
 dict* evalScriptsDict(void);
 unsigned long evalScriptsMemory(void);
+void evalScriptsGC(void);
 uint64_t evalGetCommandFlags(client *c, uint64_t orig_flags);
 uint64_t fcallGetCommandFlags(client *c, uint64_t orig_flags);
 int isInsideYieldingLongCommand(void);

tests/unit/scripting.tcl

@@ -2383,3 +2383,21 @@ start_server {tags {"scripting"}} {
         }
     }
 }
+
+start_server {tags {"scripting"}} {
+    test "LUA gc in cron" {
+        set dummy_script "--[string repeat x 40]\nreturn "
+        set n 150000
+        for {set i 0} {$i < $n} {incr i} {
+            set val "$dummy_script[format "%06d" $i]"
+            r script load $val
+        }
+
+        # we expect the gabages in the LUA VM to be collected in the cron.
+        wait_for_condition 500 10 {
+            [s used_memory_lua] < 60000000
+        } else {
+            fail "LUA gc in cron doesn't work"
+        }
+    }
+}