OpenZFS - Performance regression suite for zfstest

OpenZFS - Performance regression suite for zfstest

Author: John Wren Kennedy <john.kennedy@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Don Brady <don.brady@intel.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: David Quigley <david.quigley@intel.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Ported-by: Don Brady <don.brady@intel.com>
OpenZFS-issue: https://www.illumos.org/issues/6950
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/dcbf3bd6
Delphix-commit: https://github.com/delphix/delphix-os/commit/978ed49
Closes #4929

ZFS Test Suite Performance Regression Tests

This was pulled into OpenZFS via the compressed arc featureand was
separated out in zfsonlinux as a separate pull request from PR-4768.
It originally came in as QA-4903 in Delphix-OS from John Kennedy.

Expected Usage:

$ DISKS="sdb sdc sdd" zfs-tests.sh -r perf-regression.run

Porting Notes:
1. Added assertions in the setup script to make sure required tools
   (fio, mpstat, ...) are present.
2. For the config.json generation in perf.shlib used arcstats and
    other binaries instead of dtrace to query the values.
3. For the perf data collection:
   - use "zpool iostat -lpvyL" instead of the io.d dtrace script
    (currently not collecting zfs_read/write latency stats)
   - mpstat and iostat take different arguments
   - prefetch_io.sh is a placeholder that uses arcstats instead of
     dtrace
4. Build machines require fio, mdadm and sysstat pakage (YMMV).

Future Work:
   - Need a way to measure zfs_read and zfs_write latencies per pool.
   - Need tools to takes two sets of output and display/graph the
     differences
   - Bring over additional regression tests from Delphix