From 5cbcda073c857f9eaeebb048bee83bb4f9cf3ba3 Mon Sep 17 00:00:00 2001
From: "Maxim.Mossienko" <Maxim.Mossienko@jetbrains.com>
Date: Fri, 26 May 2017 16:16:22 +0200
Subject: [PATCH] [startup performance] lazy loading of ByteBuffer containing
 root

---
 .../com/intellij/util/io/IntToIntBtree.java   | 70 ++++++++++++-------
 1 file changed, 45 insertions(+), 25 deletions(-)

diff --git a/platform/util/src/com/intellij/util/io/IntToIntBtree.java b/platform/util/src/com/intellij/util/io/IntToIntBtree.java
index 81ae90b578ee..5d5d5f7b5b28 100644
--- a/platform/util/src/com/intellij/util/io/IntToIntBtree.java
+++ b/platform/util/src/com/intellij/util/io/IntToIntBtree.java
@@ -38,7 +38,7 @@ public class IntToIntBtree {
   private final short maxInteriorNodes;
   private final short maxLeafNodes;
   private final short maxLeafNodesInHash;
-  final BtreeIndexNodeView root;
+  final BtreeRootNode root;
   private int height;
   private int maxStepsSearchedInHash;
   private int totalHashStepsSearched;
@@ -69,12 +69,12 @@ public class IntToIntBtree {
     }
 
     storage = new ResizeableMappedFile(file, pageSize, storageLockContext, 1024 * 1024, true, IOUtil.ourByteBuffersUseNativeByteOrder);
-    root = new BtreeIndexNodeView(this);
+    root = new BtreeRootNode(this);
 
     if (initial) {
       nextPage(); // allocate root
       root.setAddress(0);
-      root.setIndexLeaf(true);
+      root.getNodeView().setIndexLeaf(true);
     }
 
     int i = (this.pageSize - BtreePage.RESERVED_META_PAGE_LEN) / BtreeIndexNodeView.INTERIOR_SIZE - 1;
@@ -133,6 +133,31 @@ public class IntToIntBtree {
     int persistInt(int offset, int value, boolean toDisk);
   }
 
+  static class BtreeRootNode {
+    int address;
+    final BtreeIndexNodeView nodeView;
+    boolean initialized;
+
+    BtreeRootNode(IntToIntBtree btree) {
+      nodeView = new BtreeIndexNodeView(btree);
+    }
+
+    void setAddress(int _address) {
+      address = _address;
+      initialized = false;
+    }
+
+    protected void syncWithStore() {
+      nodeView.setAddress(address);
+      initialized = true;
+    }
+
+    public BtreeIndexNodeView getNodeView() {
+      if (!initialized) syncWithStore();
+      return nodeView;
+    }
+  }
+
   private static boolean isPrime(int val) {
     if (val % 2 == 0) return false;
     int maxDivisor = (int)Math.sqrt(val);
@@ -226,7 +251,7 @@ public class IntToIntBtree {
   }
 
   void dumpStatistics() {
-    int leafPages = height == 3 ? pagesCount - (1 + root.getChildrenCount() + 1):height == 2 ? pagesCount - 1:1;
+    int leafPages = height == 3 ? pagesCount - (1 + root.getNodeView().getChildrenCount() + 1):height == 2 ? pagesCount - 1:1;
     long leafNodesCapacity = hashedPagesCount * maxLeafNodesInHash + (leafPages - hashedPagesCount)* maxLeafNodes;
     long leafNodesCapacity2 = leafPages * maxLeafNodes;
     int usedPercent = (int)((count * 100L) / leafNodesCapacity);
@@ -291,12 +316,16 @@ public class IntToIntBtree {
     }
 
     void setAddress(int _address) {
-      if (doSanityCheck) myAssert(_address % btree.pageSize == 0);
-      address = _address;
+      setAddressInternal(_address);
 
       syncWithStore();
     }
 
+    private final void setAddressInternal(int _address) {
+      if (doSanityCheck) myAssert(_address % btree.pageSize == 0);
+      address = _address;
+    }
+
     protected void syncWithStore() {
       PagedFileStorage pagedFileStorage = btree.storage.getPagedFileStorage();
       myAddressInBuffer = pagedFileStorage.getOffsetInPage(address);
@@ -731,7 +760,7 @@ public class IntToIntBtree {
         }
       } else {
         if (doSanityCheck) {
-          btree.root.dump("Splitting root:"+medianKey);
+          btree.root.getNodeView().dump("Splitting root:"+medianKey);
         }
 
         int newRootAddress = btree.nextPage();
@@ -744,13 +773,14 @@ public class IntToIntBtree {
         btree.root.setAddress(newRootAddress);
         parentAddress = newRootAddress;
 
-        btree.root.setChildrenCount((short)1); // btree.root becomes dirty
-        btree.root.setKeyAt(0, medianKey);
-        btree.root.setAddressAt(0, -address);
-        btree.root.setAddressAt(1, -newIndexNode.address);
+        BtreeIndexNodeView rootNodeView = btree.root.getNodeView();
+        rootNodeView.setChildrenCount((short)1); // btree.root becomes dirty
+        rootNodeView.setKeyAt(0, medianKey);
+        rootNodeView.setAddressAt(0, -address);
+        rootNodeView.setAddressAt(1, -newIndexNode.address);
 
         if (doSanityCheck) {
-          btree.root.dump("New root");
+          rootNodeView.dump("New root");
           dump("First child");
           newIndexNode.dump("Second child");
         }
@@ -941,7 +971,7 @@ public class IntToIntBtree {
       }
     }
 
-    private void dump(String s) {
+    protected void dump(String s) {
       if (doDump) {
         immediateDump(s);
       }
@@ -1124,9 +1154,9 @@ public class IntToIntBtree {
     root.syncWithStore();
 
     if (hasZeroKey) {
-      if(!processor.process(0, zeroKeyValue)) return false;
+      if (!processor.process(0, zeroKeyValue)) return false;
     }
-    return processLeafPages(root, processor);
+    return processLeafPages(root.getNodeView(), processor);
   }
 
   private boolean processLeafPages(@NotNull BtreeIndexNodeView node, @NotNull KeyValueProcessor processor) throws IOException {
@@ -1151,14 +1181,4 @@ public class IntToIntBtree {
     }
     return true;
   }
-
-  public void withStorageLock(@NotNull Runnable runnable) {
-    storage.getPagedFileStorage().lock();
-    try {
-      runnable.run();
-    }
-    finally {
-      storage.getPagedFileStorage().unlock();
-    }
-  }
 }