public void logReadingStripe(int stripeIx, long stripeOffset, long length) {
    if (log == null) return;
    int offset = this.offset;
    if (offset + 3 > log.length) return;
    log[offset] = makeIntPair(READING_STRIPE, stripeIx);
    log[offset + 1] = stripeOffset;
    log[offset + 2] = length;
    this.offset += 3;
  }
Single threaded IO trace.
Note: this can be made MTT merely by using an AtomicInteger, and storing a thread ID.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/encoded/IoTrace.java