diff --git a/src/latency.h b/src/latency.h
index 5f50392597e12899575f7d9148f29d7c5961a337..cba30391223adf0f6659f524daaa9b13301b9a76 100644
--- a/src/latency.h
+++ b/src/latency.h
@@ -35,7 +35,7 @@ void latencyAddSample(char *event, mstime_t latency);
 
 /* Add the sample only if the elapsed time is >= to the configured threshold. */
 #define latencyAddSampleIfNeeded(event,var) \
-    if (server.latency_monitor_threshold && \\
+    if (server.latency_monitor_threshold && \
         var >= server.latency_monitor_threshold) \
           latencyAddSample(event,var);
 
diff --git a/src/redis.c b/src/redis.c
index 8308cf91aacd6ce14a9aaa10cc9f3708f1765185..ac544095aea054a049e270cb834e83732ab985f0 100644
--- a/src/redis.c
+++ b/src/redis.c
@@ -112,48 +112,52 @@ struct redisCommand *commandTable;
  *    server this data. Normally no command is accepted in this condition
  *    but just a few.
  * M: Do not automatically propagate the command on MONITOR.
+ * F: Fast command: O(1) or O(log(N)) command that should never delay
+ *    its execution as long as the kernel scheduler is giving us time.
+ *    Note that commands that may trigger a DEL as a side effect (like SET)
+ *    are not fast commands.
  */
 struct redisCommand redisCommandTable[] = {
-    {"get",getCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"set",setCommand,-3,"wm",0,noPreloadGetKeys,1,1,1,0,0},
-    {"setnx",setnxCommand,3,"wm",0,noPreloadGetKeys,1,1,1,0,0},
-    {"setex",setexCommand,4,"wm",0,noPreloadGetKeys,1,1,1,0,0},
-    {"psetex",psetexCommand,4,"wm",0,noPreloadGetKeys,1,1,1,0,0},
+    {"get",getCommand,2,"rF",0,NULL,1,1,1,0,0},
+    {"set",setCommand,-3,"wm",0,NULL,1,1,1,0,0},
+    {"setnx",setnxCommand,3,"wmF",0,NULL,1,1,1,0,0},
+    {"setex",setexCommand,4,"wm",0,NULL,1,1,1,0,0},
+    {"psetex",psetexCommand,4,"wm",0,NULL,1,1,1,0,0},
     {"append",appendCommand,3,"wm",0,NULL,1,1,1,0,0},
-    {"strlen",strlenCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"del",delCommand,-2,"w",0,noPreloadGetKeys,1,-1,1,0,0},
-    {"exists",existsCommand,2,"r",0,NULL,1,1,1,0,0},
+    {"strlen",strlenCommand,2,"rF",0,NULL,1,1,1,0,0},
+    {"del",delCommand,-2,"w",0,NULL,1,-1,1,0,0},
+    {"exists",existsCommand,2,"rF",0,NULL,1,1,1,0,0},
     {"setbit",setbitCommand,4,"wm",0,NULL,1,1,1,0,0},
-    {"getbit",getbitCommand,3,"r",0,NULL,1,1,1,0,0},
+    {"getbit",getbitCommand,3,"rF",0,NULL,1,1,1,0,0},
     {"setrange",setrangeCommand,4,"wm",0,NULL,1,1,1,0,0},
     {"getrange",getrangeCommand,4,"r",0,NULL,1,1,1,0,0},
     {"substr",getrangeCommand,4,"r",0,NULL,1,1,1,0,0},
-    {"incr",incrCommand,2,"wm",0,NULL,1,1,1,0,0},
-    {"decr",decrCommand,2,"wm",0,NULL,1,1,1,0,0},
+    {"incr",incrCommand,2,"wmF",0,NULL,1,1,1,0,0},
+    {"decr",decrCommand,2,"wmF",0,NULL,1,1,1,0,0},
     {"mget",mgetCommand,-2,"r",0,NULL,1,-1,1,0,0},
-    {"rpush",rpushCommand,-3,"wm",0,NULL,1,1,1,0,0},
-    {"lpush",lpushCommand,-3,"wm",0,NULL,1,1,1,0,0},
-    {"rpushx",rpushxCommand,3,"wm",0,NULL,1,1,1,0,0},
-    {"lpushx",lpushxCommand,3,"wm",0,NULL,1,1,1,0,0},
+    {"rpush",rpushCommand,-3,"wmF",0,NULL,1,1,1,0,0},
+    {"lpush",lpushCommand,-3,"wmF",0,NULL,1,1,1,0,0},
+    {"rpushx",rpushxCommand,3,"wmF",0,NULL,1,1,1,0,0},
+    {"lpushx",lpushxCommand,3,"wmF",0,NULL,1,1,1,0,0},
     {"linsert",linsertCommand,5,"wm",0,NULL,1,1,1,0,0},
-    {"rpop",rpopCommand,2,"w",0,NULL,1,1,1,0,0},
-    {"lpop",lpopCommand,2,"w",0,NULL,1,1,1,0,0},
+    {"rpop",rpopCommand,2,"wF",0,NULL,1,1,1,0,0},
+    {"lpop",lpopCommand,2,"wF",0,NULL,1,1,1,0,0},
     {"brpop",brpopCommand,-3,"ws",0,NULL,1,1,1,0,0},
     {"brpoplpush",brpoplpushCommand,4,"wms",0,NULL,1,2,1,0,0},
     {"blpop",blpopCommand,-3,"ws",0,NULL,1,-2,1,0,0},
-    {"llen",llenCommand,2,"r",0,NULL,1,1,1,0,0},
+    {"llen",llenCommand,2,"rF",0,NULL,1,1,1,0,0},
     {"lindex",lindexCommand,3,"r",0,NULL,1,1,1,0,0},
     {"lset",lsetCommand,4,"wm",0,NULL,1,1,1,0,0},
     {"lrange",lrangeCommand,4,"r",0,NULL,1,1,1,0,0},
     {"ltrim",ltrimCommand,4,"w",0,NULL,1,1,1,0,0},
     {"lrem",lremCommand,4,"w",0,NULL,1,1,1,0,0},
     {"rpoplpush",rpoplpushCommand,3,"wm",0,NULL,1,2,1,0,0},
-    {"sadd",saddCommand,-3,"wm",0,NULL,1,1,1,0,0},
-    {"srem",sremCommand,-3,"w",0,NULL,1,1,1,0,0},
-    {"smove",smoveCommand,4,"w",0,NULL,1,2,1,0,0},
-    {"sismember",sismemberCommand,3,"r",0,NULL,1,1,1,0,0},
-    {"scard",scardCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"spop",spopCommand,2,"wRs",0,NULL,1,1,1,0,0},
+    {"sadd",saddCommand,-3,"wmF",0,NULL,1,1,1,0,0},
+    {"srem",sremCommand,-3,"wF",0,NULL,1,1,1,0,0},
+    {"smove",smoveCommand,4,"wF",0,NULL,1,2,1,0,0},
+    {"sismember",sismemberCommand,3,"rF",0,NULL,1,1,1,0,0},
+    {"scard",scardCommand,2,"rF",0,NULL,1,1,1,0,0},
+    {"spop",spopCommand,2,"wRsF",0,NULL,1,1,1,0,0},
     {"srandmember",srandmemberCommand,-2,"rR",0,NULL,1,1,1,0,0},
     {"sinter",sinterCommand,-2,"rS",0,NULL,1,-1,1,0,0},
     {"sinterstore",sinterstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
@@ -163,9 +167,9 @@ struct redisCommand redisCommandTable[] = {
     {"sdiffstore",sdiffstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
     {"smembers",sinterCommand,2,"rS",0,NULL,1,1,1,0,0},
     {"sscan",sscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
-    {"zadd",zaddCommand,-4,"wm",0,NULL,1,1,1,0,0},
-    {"zincrby",zincrbyCommand,4,"wm",0,NULL,1,1,1,0,0},
-    {"zrem",zremCommand,-3,"w",0,NULL,1,1,1,0,0},
+    {"zadd",zaddCommand,-4,"wmF",0,NULL,1,1,1,0,0},
+    {"zincrby",zincrbyCommand,4,"wmF",0,NULL,1,1,1,0,0},
+    {"zrem",zremCommand,-3,"wF",0,NULL,1,1,1,0,0},
     {"zremrangebyscore",zremrangebyscoreCommand,4,"w",0,NULL,1,1,1,0,0},
     {"zremrangebyrank",zremrangebyrankCommand,4,"w",0,NULL,1,1,1,0,0},
     {"zremrangebylex",zremrangebylexCommand,4,"w",0,NULL,1,1,1,0,0},
@@ -176,58 +180,58 @@ struct redisCommand redisCommandTable[] = {
     {"zrevrangebyscore",zrevrangebyscoreCommand,-4,"r",0,NULL,1,1,1,0,0},
     {"zrangebylex",zrangebylexCommand,-4,"r",0,NULL,1,1,1,0,0},
     {"zrevrangebylex",zrevrangebylexCommand,-4,"r",0,NULL,1,1,1,0,0},
-    {"zcount",zcountCommand,4,"r",0,NULL,1,1,1,0,0},
-    {"zlexcount",zlexcountCommand,4,"r",0,NULL,1,1,1,0,0},
+    {"zcount",zcountCommand,4,"rF",0,NULL,1,1,1,0,0},
+    {"zlexcount",zlexcountCommand,4,"rF",0,NULL,1,1,1,0,0},
     {"zrevrange",zrevrangeCommand,-4,"r",0,NULL,1,1,1,0,0},
-    {"zcard",zcardCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"zscore",zscoreCommand,3,"r",0,NULL,1,1,1,0,0},
-    {"zrank",zrankCommand,3,"r",0,NULL,1,1,1,0,0},
-    {"zrevrank",zrevrankCommand,3,"r",0,NULL,1,1,1,0,0},
+    {"zcard",zcardCommand,2,"rF",0,NULL,1,1,1,0,0},
+    {"zscore",zscoreCommand,3,"rF",0,NULL,1,1,1,0,0},
+    {"zrank",zrankCommand,3,"rF",0,NULL,1,1,1,0,0},
+    {"zrevrank",zrevrankCommand,3,"rF",0,NULL,1,1,1,0,0},
     {"zscan",zscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
-    {"hset",hsetCommand,4,"wm",0,NULL,1,1,1,0,0},
-    {"hsetnx",hsetnxCommand,4,"wm",0,NULL,1,1,1,0,0},
-    {"hget",hgetCommand,3,"r",0,NULL,1,1,1,0,0},
+    {"hset",hsetCommand,4,"wmF",0,NULL,1,1,1,0,0},
+    {"hsetnx",hsetnxCommand,4,"wmF",0,NULL,1,1,1,0,0},
+    {"hget",hgetCommand,3,"rF",0,NULL,1,1,1,0,0},
     {"hmset",hmsetCommand,-4,"wm",0,NULL,1,1,1,0,0},
     {"hmget",hmgetCommand,-3,"r",0,NULL,1,1,1,0,0},
-    {"hincrby",hincrbyCommand,4,"wm",0,NULL,1,1,1,0,0},
-    {"hincrbyfloat",hincrbyfloatCommand,4,"wm",0,NULL,1,1,1,0,0},
-    {"hdel",hdelCommand,-3,"w",0,NULL,1,1,1,0,0},
-    {"hlen",hlenCommand,2,"r",0,NULL,1,1,1,0,0},
+    {"hincrby",hincrbyCommand,4,"wmF",0,NULL,1,1,1,0,0},
+    {"hincrbyfloat",hincrbyfloatCommand,4,"wmF",0,NULL,1,1,1,0,0},
+    {"hdel",hdelCommand,-3,"wF",0,NULL,1,1,1,0,0},
+    {"hlen",hlenCommand,2,"rF",0,NULL,1,1,1,0,0},
     {"hkeys",hkeysCommand,2,"rS",0,NULL,1,1,1,0,0},
     {"hvals",hvalsCommand,2,"rS",0,NULL,1,1,1,0,0},
     {"hgetall",hgetallCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"hexists",hexistsCommand,3,"r",0,NULL,1,1,1,0,0},
+    {"hexists",hexistsCommand,3,"rF",0,NULL,1,1,1,0,0},
     {"hscan",hscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
-    {"incrby",incrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
-    {"decrby",decrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
-    {"incrbyfloat",incrbyfloatCommand,3,"wm",0,NULL,1,1,1,0,0},
+    {"incrby",incrbyCommand,3,"wmF",0,NULL,1,1,1,0,0},
+    {"decrby",decrbyCommand,3,"wmF",0,NULL,1,1,1,0,0},
+    {"incrbyfloat",incrbyfloatCommand,3,"wmF",0,NULL,1,1,1,0,0},
     {"getset",getsetCommand,3,"wm",0,NULL,1,1,1,0,0},
     {"mset",msetCommand,-3,"wm",0,NULL,1,-1,2,0,0},
     {"msetnx",msetnxCommand,-3,"wm",0,NULL,1,-1,2,0,0},
     {"randomkey",randomkeyCommand,1,"rR",0,NULL,0,0,0,0,0},
-    {"select",selectCommand,2,"rl",0,NULL,0,0,0,0,0},
-    {"move",moveCommand,3,"w",0,NULL,1,1,1,0,0},
-    {"rename",renameCommand,3,"w",0,renameGetKeys,1,2,1,0,0},
-    {"renamenx",renamenxCommand,3,"w",0,renameGetKeys,1,2,1,0,0},
-    {"expire",expireCommand,3,"w",0,NULL,1,1,1,0,0},
-    {"expireat",expireatCommand,3,"w",0,NULL,1,1,1,0,0},
-    {"pexpire",pexpireCommand,3,"w",0,NULL,1,1,1,0,0},
-    {"pexpireat",pexpireatCommand,3,"w",0,NULL,1,1,1,0,0},
+    {"select",selectCommand,2,"rlF",0,NULL,0,0,0,0,0},
+    {"move",moveCommand,3,"wF",0,NULL,1,1,1,0,0},
+    {"rename",renameCommand,3,"w",0,NULL,1,2,1,0,0},
+    {"renamenx",renamenxCommand,3,"wF",0,NULL,1,2,1,0,0},
+    {"expire",expireCommand,3,"wF",0,NULL,1,1,1,0,0},
+    {"expireat",expireatCommand,3,"wF",0,NULL,1,1,1,0,0},
+    {"pexpire",pexpireCommand,3,"wF",0,NULL,1,1,1,0,0},
+    {"pexpireat",pexpireatCommand,3,"wF",0,NULL,1,1,1,0,0},
     {"keys",keysCommand,2,"rS",0,NULL,0,0,0,0,0},
     {"scan",scanCommand,-2,"rR",0,NULL,0,0,0,0,0},
-    {"dbsize",dbsizeCommand,1,"r",0,NULL,0,0,0,0,0},
-    {"auth",authCommand,2,"rslt",0,NULL,0,0,0,0,0},
-    {"ping",pingCommand,1,"rt",0,NULL,0,0,0,0,0},
-    {"echo",echoCommand,2,"r",0,NULL,0,0,0,0,0},
+    {"dbsize",dbsizeCommand,1,"rF",0,NULL,0,0,0,0,0},
+    {"auth",authCommand,2,"rsltF",0,NULL,0,0,0,0,0},
+    {"ping",pingCommand,1,"rtF",0,NULL,0,0,0,0,0},
+    {"echo",echoCommand,2,"rF",0,NULL,0,0,0,0,0},
     {"save",saveCommand,1,"ars",0,NULL,0,0,0,0,0},
     {"bgsave",bgsaveCommand,1,"ar",0,NULL,0,0,0,0,0},
     {"bgrewriteaof",bgrewriteaofCommand,1,"ar",0,NULL,0,0,0,0,0},
     {"shutdown",shutdownCommand,-1,"arlt",0,NULL,0,0,0,0,0},
-    {"lastsave",lastsaveCommand,1,"rR",0,NULL,0,0,0,0,0},
-    {"type",typeCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"multi",multiCommand,1,"rs",0,NULL,0,0,0,0,0},
+    {"lastsave",lastsaveCommand,1,"rRF",0,NULL,0,0,0,0,0},
+    {"type",typeCommand,2,"rF",0,NULL,1,1,1,0,0},
+    {"multi",multiCommand,1,"rsF",0,NULL,0,0,0,0,0},
     {"exec",execCommand,1,"sM",0,NULL,0,0,0,0,0},
-    {"discard",discardCommand,1,"rs",0,NULL,0,0,0,0,0},
+    {"discard",discardCommand,1,"rsF",0,NULL,0,0,0,0,0},
     {"sync",syncCommand,1,"ars",0,NULL,0,0,0,0,0},
     {"psync",syncCommand,3,"ars",0,NULL,0,0,0,0,0},
     {"replconf",replconfCommand,-1,"arslt",0,NULL,0,0,0,0,0},
@@ -236,9 +240,9 @@ struct redisCommand redisCommandTable[] = {
     {"sort",sortCommand,-2,"wm",0,NULL,1,1,1,0,0},
     {"info",infoCommand,-1,"rlt",0,NULL,0,0,0,0,0},
     {"monitor",monitorCommand,1,"ars",0,NULL,0,0,0,0,0},
-    {"ttl",ttlCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"pttl",pttlCommand,2,"r",0,NULL,1,1,1,0,0},
-    {"persist",persistCommand,2,"w",0,NULL,1,1,1,0,0},
+    {"ttl",ttlCommand,2,"rF",0,NULL,1,1,1,0,0},
+    {"pttl",pttlCommand,2,"rF",0,NULL,1,1,1,0,0},
+    {"persist",persistCommand,2,"wF",0,NULL,1,1,1,0,0},
     {"slaveof",slaveofCommand,3,"ast",0,NULL,0,0,0,0,0},
     {"role",roleCommand,1,"last",0,NULL,0,0,0,0,0},
     {"debug",debugCommand,-2,"as",0,NULL,0,0,0,0,0},
@@ -247,10 +251,10 @@ struct redisCommand redisCommandTable[] = {
     {"unsubscribe",unsubscribeCommand,-1,"rpslt",0,NULL,0,0,0,0,0},
     {"psubscribe",psubscribeCommand,-2,"rpslt",0,NULL,0,0,0,0,0},
     {"punsubscribe",punsubscribeCommand,-1,"rpslt",0,NULL,0,0,0,0,0},
-    {"publish",publishCommand,3,"pltr",0,NULL,0,0,0,0,0},
+    {"publish",publishCommand,3,"pltrF",0,NULL,0,0,0,0,0},
     {"pubsub",pubsubCommand,-2,"pltrR",0,NULL,0,0,0,0,0},
-    {"watch",watchCommand,-2,"rs",0,noPreloadGetKeys,1,-1,1,0,0},
-    {"unwatch",unwatchCommand,1,"rs",0,NULL,0,0,0,0,0},
+    {"watch",watchCommand,-2,"rsF",0,NULL,1,-1,1,0,0},
+    {"unwatch",unwatchCommand,1,"rsF",0,NULL,0,0,0,0,0},
     {"restore",restoreCommand,4,"awm",0,NULL,1,1,1,0,0},
     {"migrate",migrateCommand,6,"aw",0,NULL,0,0,0,0,0},
     {"dump",dumpCommand,2,"ar",0,NULL,1,1,1,0,0},
@@ -260,13 +264,13 @@ struct redisCommand redisCommandTable[] = {
     {"evalsha",evalShaCommand,-3,"s",0,zunionInterGetKeys,0,0,0,0,0},
     {"slowlog",slowlogCommand,-2,"r",0,NULL,0,0,0,0,0},
     {"script",scriptCommand,-2,"ras",0,NULL,0,0,0,0,0},
-    {"time",timeCommand,1,"rR",0,NULL,0,0,0,0,0},
+    {"time",timeCommand,1,"rRF",0,NULL,0,0,0,0,0},
     {"bitop",bitopCommand,-4,"wm",0,NULL,2,-1,1,0,0},
     {"bitcount",bitcountCommand,-2,"r",0,NULL,1,1,1,0,0},
     {"bitpos",bitposCommand,-3,"r",0,NULL,1,1,1,0,0},
     {"command",commandCommand,0,"rlt",0,NULL,0,0,0,0,0},
     {"pfselftest",pfselftestCommand,1,"r",0,NULL,0,0,0,0,0},
-    {"pfadd",pfaddCommand,-2,"wm",0,NULL,1,1,1,0,0},
+    {"pfadd",pfaddCommand,-2,"wmF",0,NULL,1,1,1,0,0},
     {"pfcount",pfcountCommand,-2,"w",0,NULL,1,1,1,0,0},
     {"pfmerge",pfmergeCommand,-2,"wm",0,NULL,1,-1,1,0,0},
     {"pfdebug",pfdebugCommand,-3,"w",0,NULL,0,0,0,0,0}
@@ -1761,6 +1765,7 @@ void populateCommandTable(void) {
             case 'l': c->flags |= REDIS_CMD_LOADING; break;
             case 't': c->flags |= REDIS_CMD_STALE; break;
             case 'M': c->flags |= REDIS_CMD_SKIP_MONITOR; break;
+            case 'F': c->flags |= REDIS_CMD_FAST; break;
             default: redisPanic("Unsupported command flag"); break;
             }
             f++;
@@ -1925,8 +1930,12 @@ void call(redisClient *c, int flags) {
 
     /* Log the command into the Slow log if needed, and populate the
      * per-command statistics that we show in INFO commandstats. */
-    if (flags & REDIS_CALL_SLOWLOG && c->cmd->proc != execCommand)
+    if (flags & REDIS_CALL_SLOWLOG && c->cmd->proc != execCommand) {
+        char *latency_event = (c->cmd->flags & REDIS_CMD_FAST) ?
+                              "fast-command" : "command";
+        latencyAddSampleIfNeeded(latency_event,duration);
         slowlogPushEntryIfNeeded(c->argv,c->argc,duration);
+    }
     if (flags & REDIS_CALL_STATS) {
         c->cmd->microseconds += duration;
         c->cmd->calls++;
@@ -2303,6 +2312,7 @@ void addReplyCommand(redisClient *c, struct redisCommand *cmd) {
         flagcount += addReplyCommandFlag(c,cmd,REDIS_CMD_LOADING, "loading");
         flagcount += addReplyCommandFlag(c,cmd,REDIS_CMD_STALE, "stale");
         flagcount += addReplyCommandFlag(c,cmd,REDIS_CMD_SKIP_MONITOR, "skip_monitor");
+        flagcount += addReplyCommandFlag(c,cmd,REDIS_CMD_FAST, "fast");
         if (cmd->getkeys_proc) {
             addReplyStatus(c, "movablekeys");
             flagcount += 1;
diff --git a/src/redis.h b/src/redis.h
index 8a1babb0f5861d4b4608be0fe73819a565e1a92f..44e0bbe5914f78dad8563f516a12a0c3bbe9ac52 100644
--- a/src/redis.h
+++ b/src/redis.h
@@ -165,6 +165,8 @@ typedef long long mstime_t; /* millisecond time type. */
 #define REDIS_CMD_LOADING 512               /* "l" flag */
 #define REDIS_CMD_STALE 1024                /* "t" flag */
 #define REDIS_CMD_SKIP_MONITOR 2048         /* "M" flag */
+#define REDIS_CMD_ASKING 4096               /* "k" flag */
+#define REDIS_CMD_FAST 8192                 /* "F" flag */
 
 /* Object types */
 #define REDIS_STRING 0