[HBASE-22802] Avoid temp ByteBuffer allocation in FileIOEngine#read

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 2.3.0
• Component/s: BucketCache
• Hadoop Flags: Reviewed

Release Note

HBASE-21879 introduces a utility class (org.apache.hadoop.hbase.io.ByteBuffAllocator) used for allocating/freeing ByteBuffers from/to NIO ByteBuffer pool, when BucketCache enabled with file or mmap engine, we will use this ByteBuffer pool to avoid temp ByteBuffer allocation a lot.

• Assignee: chenxu
• Reporter: chenxu
• Created: 06/Aug/19 15:15
• Updated: 09/Sep/19 15:20
• Resolved: 09/Sep/19 09:54

Description

a temp ByteBuffer was allocated each time FileIOEngine#read was called

public Cacheable read(BucketEntry be) throws IOException {
  long offset = be.offset();
  int length = be.getLength();
  Preconditions.checkArgument(length >= 0, "Length of read can not be less than 0.");
  ByteBuffer dstBuffer = ByteBuffer.allocate(length);
  ...
}

we can avoid this by use of ByteBuffAllocator#allocate(length) after HBASE-21879

Issue Links

• Blocked: HBASE-22996 refact MultiByteBuff, combine the buffsIterator and curItem & curItemIndex into one iterator
• links to: GitHub Pull Request #479
• links to: GitHub Pull Request #583