From c426d85c4c877a21c959b306b81d8df46259cbd6 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Mon, 30 Jul 2018 13:37:30 +0200
Subject: [PATCH] Control dynamic HZ via server configuration.

---
 src/server.c | 17 +++++++++++------
 src/server.h |  2 ++
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/server.c b/src/server.c
index 965cae96..23450c8f 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1096,14 +1096,18 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
     /* Update the time cache. */
     updateCachedTime();
 
+    server.hz = server.config_hz;
     /* Adapt the server.hz value to the number of configured clients. If we have
      * many clients, we want to call serverCron() with an higher frequency. */
-    server.hz = server.config_hz;
-    while (listLength(server.clients) / server.hz > MAX_CLIENTS_PER_CLOCK_TICK) {
-        server.hz *= 2;
-        if (server.hz > CONFIG_MAX_HZ) {
-            server.hz = CONFIG_MAX_HZ;
-            break;
+    if (server.dynamic_hz) {
+        while (listLength(server.clients) / server.hz >
+               MAX_CLIENTS_PER_CLOCK_TICK)
+        {
+            server.hz *= 2;
+            if (server.hz > CONFIG_MAX_HZ) {
+                server.hz = CONFIG_MAX_HZ;
+                break;
+            }
         }
     }
 
@@ -1524,6 +1528,7 @@ void initServerConfig(void) {
     server.configfile = NULL;
     server.executable = NULL;
     server.config_hz = CONFIG_DEFAULT_HZ;
+    server.dynamic_hz = CONFIG_DEFAULT_DYNAMIC_HZ;
     server.arch_bits = (sizeof(long) == 8) ? 64 : 32;
     server.port = CONFIG_DEFAULT_SERVER_PORT;
     server.tcp_backlog = CONFIG_DEFAULT_TCP_BACKLOG;
diff --git a/src/server.h b/src/server.h
index 4d63faa6..21e4c427 100644
--- a/src/server.h
+++ b/src/server.h
@@ -78,6 +78,7 @@ typedef long long mstime_t; /* millisecond time type. */
 #define C_ERR                   -1
 
 /* Static server configuration */
+#define CONFIG_DEFAULT_DYNAMIC_HZ 1             /* Adapt hz to # of clients.*/
 #define CONFIG_DEFAULT_HZ        10             /* Time interrupt calls/sec. */
 #define CONFIG_MIN_HZ            1
 #define CONFIG_MAX_HZ            500
@@ -925,6 +926,7 @@ struct redisServer {
     char *configfile;           /* Absolute config file path, or NULL */
     char *executable;           /* Absolute executable file path. */
     char **exec_argv;           /* Executable argv vector (copy). */
+    int dynamic_hz;             /* Change hz value depending on # of clients. */
     int config_hz;              /* Configured HZ value. May be different than
                                    the actual 'hz' field value if dynamic-hz
                                    is enabled. */