diff --git a/core/src/main/scala/kafka/log/AbstractIndex.scala b/core/src/main/scala/kafka/log/AbstractIndex.scala
index 05237c44193fc..bae5d84d0fceb 100644
--- a/core/src/main/scala/kafka/log/AbstractIndex.scala
+++ b/core/src/main/scala/kafka/log/AbstractIndex.scala
@@ -175,7 +175,8 @@ abstract class AbstractIndex[K, V](@volatile var file: File, val baseOffset: Lon
       val roundedNewSize = roundDownToExactMultiple(newSize, entrySize)
 
       if (_length == roundedNewSize) {
-        debug(s"Index ${file.getAbsolutePath} was not resized because it already has size $roundedNewSize")
+        if (isDebugEnabled)
+          debug(s"Index ${file.getAbsolutePath} was not resized because it already has size $roundedNewSize")
         false
       } else {
         val raf = new RandomAccessFile(file, "rw")
@@ -190,8 +191,9 @@ abstract class AbstractIndex[K, V](@volatile var file: File, val baseOffset: Lon
           mmap = raf.getChannel().map(FileChannel.MapMode.READ_WRITE, 0, roundedNewSize)
           _maxEntries = mmap.limit() / entrySize
           mmap.position(position)
-          debug(s"Resized ${file.getAbsolutePath} to $roundedNewSize, position is ${mmap.position()} " +
-            s"and limit is ${mmap.limit()}")
+          if (isDebugEnabled)
+            debug(s"Resized ${file.getAbsolutePath} to $roundedNewSize, position is ${mmap.position()} " +
+                  s"and limit is ${mmap.limit()}")
           true
         } finally {
           CoreUtils.swallow(raf.close(), AbstractIndex)
diff --git a/core/src/main/scala/kafka/log/LogSegment.scala b/core/src/main/scala/kafka/log/LogSegment.scala
index f25813903225d..1b60ac0af5bf8 100755
--- a/core/src/main/scala/kafka/log/LogSegment.scala
+++ b/core/src/main/scala/kafka/log/LogSegment.scala
@@ -43,8 +43,8 @@ import scala.math._
  * A segment with a base offset of [base_offset] would be stored in two files, a [base_offset].index and a [base_offset].log file.
  *
  * @param log The file records containing log entries
- * @param offsetIndex The offset index
- * @param timeIndex The timestamp index
+ * @param lazyOffsetIndex The offset index
+ * @param lazyTimeIndex The timestamp index
  * @param txnIndex The transaction index
  * @param baseOffset A lower bound on the offsets in this segment
  * @param indexIntervalBytes The approximate number of bytes between entries in the index
diff --git a/core/src/main/scala/kafka/log/OffsetIndex.scala b/core/src/main/scala/kafka/log/OffsetIndex.scala
index d043d0a50271a..93a1c036b39d3 100755
--- a/core/src/main/scala/kafka/log/OffsetIndex.scala
+++ b/core/src/main/scala/kafka/log/OffsetIndex.scala
@@ -59,8 +59,9 @@ class OffsetIndex(_file: File, baseOffset: Long, maxIndexSize: Int = -1, writabl
   /* the last offset in the index */
   private[this] var _lastOffset = lastEntry.offset
 
-  debug(s"Loaded index file ${file.getAbsolutePath} with maxEntries = $maxEntries, " +
-    s"maxIndexSize = $maxIndexSize, entries = ${_entries}, lastOffset = ${_lastOffset}, file position = ${mmap.position()}")
+  if (isDebugEnabled)
+    debug(s"Loaded index file ${file.getAbsolutePath} with maxEntries = $maxEntries, " +
+      s"maxIndexSize = $maxIndexSize, entries = ${_entries}, lastOffset = ${_lastOffset}, file position = ${mmap.position()}")
 
   /**
    * The last entry in the index
@@ -136,13 +137,14 @@ class OffsetIndex(_file: File, baseOffset: Long, maxIndexSize: Int = -1, writabl
 
   /**
    * Append an entry for the given offset/location pair to the index. This entry must have a larger offset than all subsequent entries.
-   * @throws IndexOffsetOverflowException if the offset causes index offset to overflow
+   * @throws kafka.common.IndexOffsetOverflowException#IndexOffsetOverflowException if the offset causes index offset to overflow
    */
   def append(offset: Long, position: Int) {
     inLock(lock) {
       require(!isFull, "Attempt to append to a full index (size = " + _entries + ").")
       if (_entries == 0 || offset > _lastOffset) {
-        trace(s"Adding index entry $offset => $position to ${file.getAbsolutePath}")
+        if (isTraceEnabled)
+          trace(s"Adding index entry $offset => $position to ${file.getAbsolutePath}")
         mmap.putInt(relativeOffset(offset))
         mmap.putInt(position)
         _entries += 1
@@ -186,8 +188,9 @@ class OffsetIndex(_file: File, baseOffset: Long, maxIndexSize: Int = -1, writabl
       _entries = entries
       mmap.position(_entries * entrySize)
       _lastOffset = lastEntry.offset
-      debug(s"Truncated index ${file.getAbsolutePath} to $entries entries;" +
-        s" position is now ${mmap.position()} and last offset is now ${_lastOffset}")
+      if (isDebugEnabled)
+        debug(s"Truncated index ${file.getAbsolutePath} to $entries entries;" +
+              s" position is now ${mmap.position()} and last offset is now ${_lastOffset}")
     }
   }
 
diff --git a/core/src/main/scala/kafka/log/TimeIndex.scala b/core/src/main/scala/kafka/log/TimeIndex.scala
index f9bc929178ad4..b2bafeb82fc02 100644
--- a/core/src/main/scala/kafka/log/TimeIndex.scala
+++ b/core/src/main/scala/kafka/log/TimeIndex.scala
@@ -58,8 +58,9 @@ class TimeIndex(_file: File, baseOffset: Long, maxIndexSize: Int = -1, writable:
 
   override def entrySize = 12
 
-  debug(s"Loaded index file ${file.getAbsolutePath} with maxEntries = $maxEntries, maxIndexSize = $maxIndexSize," +
-    s" entries = ${_entries}, lastOffset = ${_lastEntry}, file position = ${mmap.position()}")
+  if (isDebugEnabled)
+    debug(s"Loaded index file ${file.getAbsolutePath} with maxEntries = $maxEntries, maxIndexSize = $maxIndexSize," +
+          s" entries = ${_entries}, lastOffset = ${_lastEntry}, file position = ${mmap.position()}")
 
   // We override the full check to reserve the last time index entry slot for the on roll call.
   override def isFull: Boolean = entries >= maxEntries - 1
@@ -120,17 +121,20 @@ class TimeIndex(_file: File, baseOffset: Long, maxIndexSize: Int = -1, writable:
       // because that could happen in the following two scenarios:
       // 1. A log segment is closed.
       // 2. LogSegment.onBecomeInactiveSegment() is called when an active log segment is rolled.
-      if (_entries != 0 && offset < lastEntry.offset)
-        throw new InvalidOffsetException(s"Attempt to append an offset ($offset) to slot ${_entries} no larger than" +
-          s" the last offset appended (${lastEntry.offset}) to ${file.getAbsolutePath}.")
-      if (_entries != 0 && timestamp < lastEntry.timestamp)
-        throw new IllegalStateException(s"Attempt to append a timestamp ($timestamp) to slot ${_entries} no larger" +
-          s" than the last timestamp appended (${lastEntry.timestamp}) to ${file.getAbsolutePath}.")
+      if (_entries != 0) {
+        if (offset < lastEntry.offset)
+          throw new InvalidOffsetException(s"Attempt to append an offset ($offset) to slot ${_entries} no larger than" +
+                                           s" the last offset appended (${lastEntry.offset}) to ${file.getAbsolutePath}.")
+        if (timestamp < lastEntry.timestamp)
+          throw new IllegalStateException(s"Attempt to append a timestamp ($timestamp) to slot ${_entries} no larger" +
+                                          s" than the last timestamp appended (${lastEntry.timestamp}) to ${file.getAbsolutePath}.")
+      }
       // We only append to the time index when the timestamp is greater than the last inserted timestamp.
       // If all the messages are in message format v0, the timestamp will always be NoTimestamp. In that case, the time
       // index will be empty.
       if (timestamp > lastEntry.timestamp) {
-        trace(s"Adding index entry $timestamp => $offset to ${file.getAbsolutePath}.")
+        if (isTraceEnabled)
+          trace(s"Adding index entry $timestamp => $offset to ${file.getAbsolutePath}.")
         mmap.putLong(timestamp)
         mmap.putInt(relativeOffset(offset))
         _entries += 1
@@ -204,7 +208,8 @@ class TimeIndex(_file: File, baseOffset: Long, maxIndexSize: Int = -1, writable:
       _entries = entries
       mmap.position(_entries * entrySize)
       _lastEntry = lastEntryFromIndexFile
-      debug(s"Truncated index ${file.getAbsolutePath} to $entries entries; position is now ${mmap.position()} and last entry is now ${_lastEntry}")
+      if (isDebugEnabled)
+        debug(s"Truncated index ${file.getAbsolutePath} to $entries entries; position is now ${mmap.position()} and last entry is now ${_lastEntry}")
     }
   }