[TEZ-2881] Fix the InputBuffer bottleneck during the in-memory spill merge

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 0.8.0-alpha
• Target Version/s: 0.8.1-alpha
• Assignee: Gopal Vijayaraghavan
• Reporter: Gopal Vijayaraghavan
• Created: 10/Oct/15 11:33
• Updated: 10/Oct/15 12:07
• Resolved: 10/Oct/15 12:07

Description

  public void reset(ByteBuffer b, int start, int length) {
      resize(length);
      b.position(start);
      b.get(buffer, 0, length);
      super.reset(buffer, 0, length);
    }

hits cpu-mem bandwidth & is mostly stalled waiting for the data.

Remove this dirty write and switch over to access buffers directly.