Offload updating cached time to dedicated thread

Former-commit-id: 9bfc8a43952481b5b54a7b051d44b8bece4a18dd

src/blocked.cpp

@@ -525,7 +525,6 @@ void handleClientsBlockedOnKeys(void) {
              * lookup, invalidating the first one.
              * See https://github.com/antirez/redis/pull/6554. */
             serverTL->fixed_time_expire++;
-            updateCachedTime(0);
 
             /* Serve clients blocked on the key. */
             robj *o = lookupKeyWrite(rl->db,rl->key);

src/rdb.cpp

@@ -2341,10 +2341,6 @@ void rdbLoadProgressCallback(rio *r, const void *buf, size_t len) {
         (g_pserver->loading_process_events_interval_keys &&
         (r->keys_since_last_callback >= g_pserver->loading_process_events_interval_keys)))
     {
-        /* The DB can take some non trivial amount of time to load. Update
-         * our cached time since it is used to create and update the last
-         * interaction time with clients and for other important things. */
-        updateCachedTime(0);
         listIter li;
         listNode *ln;
         listRewind(g_pserver->masters, &li);

src/server.cpp

@@ -2002,7 +2002,7 @@ void databasesCron(bool fMainThread) {
  * info or not using the 'update_daylight_info' argument. Normally we update
  * such info only when calling this function from serverCron() but not when
  * calling it from call(). */
-void updateCachedTime(int update_daylight_info) {
+void updateCachedTime() {
     long long t = ustime();
     __atomic_store(&g_pserver->ustime, &t, __ATOMIC_RELAXED);
     t /= 1000;
@@ -2015,12 +2015,10 @@ void updateCachedTime(int update_daylight_info) {
      * context is safe since we will never fork() while here, in the main
      * thread. The logging function will call a thread safe version of
      * localtime that has no locks. */
-    if (update_daylight_info) {
+    struct tm tm;
-        struct tm tm;
+    time_t ut = g_pserver->unixtime;
-        time_t ut = g_pserver->unixtime;
+    localtime_r(&ut,&tm);
-        localtime_r(&ut,&tm);
+    __atomic_store(&g_pserver->daylight_active, &tm.tm_isdst, __ATOMIC_RELAXED);
-        __atomic_store(&g_pserver->daylight_active, &tm.tm_isdst, __ATOMIC_RELAXED);
-    }
 }
 
 void checkChildrenDone(void) {
@@ -2172,9 +2170,6 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
      * handler if we don't return here fast enough. */
     if (g_pserver->watchdog_period) watchdogScheduleSignal(g_pserver->watchdog_period);
 
-    /* Update the time cache. */
-    updateCachedTime(1);
-
     /* Unpause clients if enough time has elapsed */
     unpauseClientsIfNecessary();
 
@@ -2812,7 +2807,7 @@ void initMasterInfo(redisMaster *master)
 void initServerConfig(void) {
     int j;
 
-    updateCachedTime(true);
+    updateCachedTime();
     getRandomHexChars(g_pserver->runid,CONFIG_RUN_ID_SIZE);
     g_pserver->runid[CONFIG_RUN_ID_SIZE] = '\0';
     changeReplicationId();
@@ -3915,7 +3910,6 @@ void call(client *c, int flags) {
 
     /* Call the command. */
     dirty = g_pserver->dirty;
-    updateCachedTime(0);
     incrementMvccTstamp();
     start = g_pserver->ustime;
     try {
@@ -6072,6 +6066,13 @@ void OnTerminate()
     serverPanic("std::teminate() called");
 }
 
+void *timeThreadMain(void*) {
+    while (true) {
+        updateCachedTime();
+        usleep(1);
+    }
+} 
+
 void *workerThreadMain(void *parg)
 {
     int iel = (int)((int64_t)parg);
@@ -6419,6 +6420,8 @@ int main(int argc, char **argv) {
     setOOMScoreAdj(-1);
     serverAssert(cserver.cthreads > 0 && cserver.cthreads <= MAX_EVENT_LOOPS);
 
+    pthread_create(&cserver.time_thread_id, nullptr, timeThreadMain, nullptr);
+
     pthread_attr_t tattr;
     pthread_attr_init(&tattr);
     pthread_attr_setstacksize(&tattr, 1 << 23); // 8 MB

src/server.h

@@ -1920,6 +1920,7 @@ struct redisServerConst {
     pid_t pid;                  /* Main process pid. */
     time_t stat_starttime;          /* Server start time */
     pthread_t main_thread_id;         /* Main thread id */
+    pthread_t time_thread_id;
     char *configfile;           /* Absolute config file path, or NULL */
     char *executable;           /* Absolute executable file path. */
     char **exec_argv;           /* Executable argv vector (copy). */
@@ -2965,7 +2966,7 @@ void populateCommandTable(void);
 void resetCommandTableStats(void);
 void adjustOpenFilesLimit(void);
 void closeListeningSockets(int unlink_unix_socket);
-void updateCachedTime(int update_daylight_info);
+void updateCachedTime();
 void resetServerStats(void);
 void activeDefragCycle(void);
 unsigned int getLRUClock(void);