From 11e7cb8bca225d50e4cc5135a83eb10b2b4c3d67 Mon Sep 17 00:00:00 2001
From: godotg <jaysunxiao.gmail.com>
Date: Fri, 24 Feb 2023 23:11:54 +0800
Subject: [PATCH] perf[time]: volatile reduces the cache hit ratio of the CPU

---
 .../main/java/com/zfoo/scheduler/manager/SchedulerBus.java | 2 --
 .../src/main/java/com/zfoo/scheduler/util/TimeUtils.java   | 7 ++++---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/scheduler/src/main/java/com/zfoo/scheduler/manager/SchedulerBus.java b/scheduler/src/main/java/com/zfoo/scheduler/manager/SchedulerBus.java
index d027d8e6..93aec1cc 100644
--- a/scheduler/src/main/java/com/zfoo/scheduler/manager/SchedulerBus.java
+++ b/scheduler/src/main/java/com/zfoo/scheduler/manager/SchedulerBus.java
@@ -68,8 +68,6 @@ public abstract class SchedulerBus {
                 logger.error("scheduler triggers an error.", e);
             }
         }, 0, TimeUtils.MILLIS_PER_SECOND, TimeUnit.MILLISECONDS);
-
-        executor.scheduleAtFixedRate(TimeUtils::currentTimeMillis, 0, 20, TimeUnit.MILLISECONDS);
     }
 
     public static class SchedulerThreadFactory implements ThreadFactory {
diff --git a/scheduler/src/main/java/com/zfoo/scheduler/util/TimeUtils.java b/scheduler/src/main/java/com/zfoo/scheduler/util/TimeUtils.java
index 4c4a4298..4192c173 100644
--- a/scheduler/src/main/java/com/zfoo/scheduler/util/TimeUtils.java
+++ b/scheduler/src/main/java/com/zfoo/scheduler/util/TimeUtils.java
@@ -83,7 +83,8 @@ public abstract class TimeUtils {
         SchedulerBus.refreshMinTriggerTimestamp();
     }
 
-    private static volatile long timestamp = System.currentTimeMillis();
+    // volatile reduces the cache hit ratio of the CPU
+    private static long timestamp = System.currentTimeMillis();
 
     /**
      * 获取精确的时间戳
@@ -94,9 +95,9 @@ public abstract class TimeUtils {
     }
 
     /**
-     * 获取最多只有20ms延迟的粗略时间戳，适用于对时间精度要求不高的场景，最多只有20ms误差
+     * CN：获取最多只有一秒延迟的粗略时间戳，适用于对时间精度要求不高的场景，比System.currentTimeMillis()的性能高10倍
      * <p>
-     * 比System.currentTimeMillis()的性能高10倍
+     * EN：Obtain a coarse timestamp with a delay of up to one second, which is suitable for scenarios that do not require high time accuracy
      */
     public static long now() {
         return timestamp;