From e9ca031d7652ea8dee9f7f3671a607ed21aaa6b3 Mon Sep 17 00:00:00 2001
From: at055612 <22818309+at055612@users.noreply.github.com>
Date: Thu, 14 Dec 2023 12:05:32 +0000
Subject: [PATCH] Add minor perf optimisation ByteBufferPoolImpl4

---
 .../bytebuffer/ByteBufferPoolImpl4.java       | 17 ++++++++++--
 .../bytebuffer/TestByteBufferPoolImpl4.java   | 26 +++++++++++++++++++
 unreleased_changes/20231214_120431_673__0.md  | 19 ++++++++++++++
 3 files changed, 60 insertions(+), 2 deletions(-)
 create mode 100644 unreleased_changes/20231214_120431_673__0.md

diff --git a/stroom-lmdb/src/main/java/stroom/bytebuffer/ByteBufferPoolImpl4.java b/stroom-lmdb/src/main/java/stroom/bytebuffer/ByteBufferPoolImpl4.java
index d18e04b70b2..513f87327e4 100644
--- a/stroom-lmdb/src/main/java/stroom/bytebuffer/ByteBufferPoolImpl4.java
+++ b/stroom-lmdb/src/main/java/stroom/bytebuffer/ByteBufferPoolImpl4.java
@@ -75,6 +75,10 @@ public class ByteBufferPoolImpl4 implements ByteBufferPool {
 
     // If no count is provided for a buffer size in the config then this value is used.
     private static final int DEFAULT_MAX_BUFFERS_PER_QUEUE = 50;
+    // The offset for a one byte buffer
+    private static final int ONE_BYTE_BUFFER_OFFSET = 0;
+    // The offset for a ten byte buffer
+    private static final int TEN_BYTE_BUFFER_OFFSET = 1;
 
     // In each of these collections, the index/offset is the log10 of the buffer size,
     // i.e. 1 => 0, 10 => 1, 100 => 2 etc.
@@ -523,8 +527,17 @@ private ByteBuffer createNewBufferIfAllowed(final int offset) {
         return byteBuffer;
     }
 
-    private int getOffset(final int minCapacity) {
-        return (int) Math.ceil(Math.log10(minCapacity));
+    // Pkg private for testing
+    static int getOffset(final int minCapacity) {
+        if (minCapacity <= 10) {
+            // Minor optimisation as a lot of the requests for buffers will be for int/longs
+            // so this saves a bit of maths.
+            return minCapacity <= 1
+                    ? ONE_BYTE_BUFFER_OFFSET
+                    : TEN_BYTE_BUFFER_OFFSET;
+        } else {
+            return (int) Math.ceil(Math.log10(minCapacity));
+        }
     }
 
     private int getNextOffset(final int offset) {
diff --git a/stroom-lmdb/src/test/java/stroom/bytebuffer/TestByteBufferPoolImpl4.java b/stroom-lmdb/src/test/java/stroom/bytebuffer/TestByteBufferPoolImpl4.java
index e1a4fdfa418..2091cc1f11a 100644
--- a/stroom-lmdb/src/test/java/stroom/bytebuffer/TestByteBufferPoolImpl4.java
+++ b/stroom-lmdb/src/test/java/stroom/bytebuffer/TestByteBufferPoolImpl4.java
@@ -1,7 +1,11 @@
 package stroom.bytebuffer;
 
+import stroom.test.common.TestUtil;
+
 import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.DynamicTest;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -13,6 +17,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
+import java.util.stream.Stream;
 
 class TestByteBufferPoolImpl4 {
 
@@ -328,4 +333,25 @@ void testIsPowerOf10() {
             i *= 10;
         }
     }
+
+    @TestFactory
+    Stream<DynamicTest> testGetOffset() {
+        return TestUtil.buildDynamicTestStream()
+                .withInputAndOutputType(int.class)
+                .withSingleArgTestFunction(ByteBufferPoolImpl4::getOffset)
+                .withSimpleEqualityAssertion()
+                .addCase(-1, 0)
+                .addCase(0, 0)
+                .addCase(1, 0)
+                .addCase(2, 1)
+                .addCase(10, 1)
+                .addCase(11, 2)
+                .addCase(100, 2)
+                .addCase(101, 3)
+                .addCase(1000, 3)
+                .addCase(1001, 4)
+                .addCase(10000, 4)
+                .addCase(10001, 5)
+                .build();
+    }
 }
diff --git a/unreleased_changes/20231214_120431_673__0.md b/unreleased_changes/20231214_120431_673__0.md
new file mode 100644
index 00000000000..d608bf23426
--- /dev/null
+++ b/unreleased_changes/20231214_120431_673__0.md
@@ -0,0 +1,19 @@
+* Add minor performance optimisation to the byte buffer pool used by the reference data store.
+
+
+```sh
+# ONLY the top line will be included as a change entry in the CHANGELOG.
+# The entry should be in GitHub flavour markdown and should be written on a SINGLE
+# line with no hard breaks. You can have multiple change files for a single GitHub issue.
+# The  entry should be written in the imperative mood, i.e. 'Fix nasty bug' rather than
+# 'Fixed nasty bug'.
+#
+# Examples of acceptable entries are:
+#
+#
+# * Issue **123** : Fix bug with an associated GitHub issue in this repository
+#
+# * Issue **namespace/other-repo#456** : Fix bug with an associated GitHub issue in another repository
+#
+# * Fix bug with no associated GitHub issue.
+```