From 1c23fc14be8a0ac9542f1412448c4d896756ba01 Mon Sep 17 00:00:00 2001
From: Keuin <keuinx@gmail.com>
Date: Fri, 22 Jan 2021 18:59:47 +0800
Subject: Speed up the incremental backup by using multiple CPU cores if
 available (use multiple threads to calculate the hash).

---
 .../keuin/kbackupfabric/util/ThreadingUtil.java    | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 src/main/java/com/keuin/kbackupfabric/util/ThreadingUtil.java

(limited to 'src/main/java/com/keuin/kbackupfabric/util/ThreadingUtil.java')

diff --git a/src/main/java/com/keuin/kbackupfabric/util/ThreadingUtil.java b/src/main/java/com/keuin/kbackupfabric/util/ThreadingUtil.java
new file mode 100644
index 0000000..b270895
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/ThreadingUtil.java
@@ -0,0 +1,22 @@
+package com.keuin.kbackupfabric.util;
+
+public class ThreadingUtil {
+    public static int getRecommendedThreadCount() {
+        int coreCount = Runtime.getRuntime().availableProcessors();
+
+        // if the cores are too few, we regress to single thread
+        if (coreCount <= 2)
+            return 1;
+
+        // we have multiple cores, but not too many
+        if (coreCount == 3)
+            return 2;
+
+        // if we have multiple core, but not too many, we use a half
+        if (coreCount <= 6) // 4, 5, 6 -> 3, 3, 4
+            return (coreCount + 2) / 2;
+
+        // cores are sufficient, we use almost all of them, except a fixed count remained for the OS
+        return coreCount - 2;
+    }
+}
-- 
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