Update cached time during slow scripts & transactions

Commands may use cached time when the precision is not vital. It is
a good idea to refresh it from time to time during the execution of long
running scripts or transactions composed of quite a lot of commands.

Author: antirez

src/multi.c

@@ -162,6 +162,10 @@ void execCommand(redisClient *c) {
         c->mstate.commands[j].argc = c->argc;
         c->mstate.commands[j].argv = c->argv;
         c->mstate.commands[j].cmd = c->cmd;
+
+        /* From time to time, update the cached time so that if the transaction
+         * is huge, we'll have a chance to have more updated time info. */
+        if (j && j % 10000) updateCachedTime();
     }
     c->argv = orig_argv;
     c->argc = orig_argc;

src/scripting.c

@@ -546,7 +546,8 @@ void luaMaskCountHook(lua_State *lua, lua_Debug *ar) {
     REDIS_NOTUSED(ar);
     REDIS_NOTUSED(lua);
 
-    elapsed = mstime() - server.lua_time_start;
+    updateCachedTime();
+    elapsed = server.mstime - server.lua_time_start;
     if (elapsed >= server.lua_time_limit && server.lua_timedout == 0) {
         redisLog(REDIS_WARNING,"Lua slow script detected: still in execution after %lld milliseconds. You can try killing the script using the SCRIPT KILL command.",elapsed);
         server.lua_timedout = 1;