utilities for block layer IO tracing

 blktrace is a block layer IO tracing mechanism which provides detailed
 information about request queue operations up to user space. There are
 three major components that are provided:
 .
 blktrace: A utility which transfers event traces from the kernel
 into either long-term on-disk storage, or provides direct formatted
 output (via blkparse).
 .
 blkparse: A utility which formats events stored in files, or when
 run in live mode directly outputs data collected by blktrace.
 .
 iowatcher: A utility to visualize block I/O patterns. It generates graphs
 from blktrace runs to help visualize IO patterns and performance. It can
 plot multiple blktrace runs together, making it easy to compare the
 differences between different benchmark runs.