Merge tag 'perf-core-for-mingo-20160510' of git://git.kernel.org/pub/scm/linux/kernel...

Pull perf/core improvements and fixes from Arnaldo Carvalho de Melo:

User visible changes:

- Recording 'dwarf' callchains do not need DWARF unwinding support (He Kuang)

- Print recently added perf_event_attr.write_backward bit flag in -vv
  verbose mode (Arnaldo Carvalho de Melo)

- Fix incorrect python db-export error message in 'perf script' (Chris Phlipot)

- Fix handling of zero-length symbols (Chris Phlipot)

- perf stat: Scale values by unit before metrics (Andi Kleen)

Infrastructure changes:

- Rewrite strbuf not to die(), making tools using it to check its
  return value instead (Masami Hiramatsu)

- Support reading from backward ring buffer, add a 'perf test' entry
  for it (Wang Nan)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>