Currently, the callchains are displayed using a constant left
margin. So depending on the current sort dimension
configuration, callchains may appear to be well attached to the
first sort dimension column field which is mostly the case,
except when the first dimension of sorting is done by comm,
because these are right aligned.

This patch binds the callchain to the first letter in the first
column, whatever type of column it is (dso, comm, symbol).
Before:

     0.80%             perf  [k] __lock_acquire
             __lock_acquire
             lock_acquire
             |
             |--58.33%-- _spin_lock
             |          |
             |          |--28.57%-- inotify_should_send_event
             |          |          fsnotify
             |          |          __fsnotify_parent

After:

     0.80%             perf  [k] __lock_acquire
                       __lock_acquire
                       lock_acquire
                       |
                       |--58.33%-- _spin_lock
                       |          |
                       |          |--28.57%-- inotify_should_send_event
                       |          |          fsnotify
                       |          |          __fsnotify_parent

Also, for clarity, we don't put anymore the callchain as is but:

- If we have a top level ancestor in the callchain, start it
  with a first ascii hook.

  Before:

     0.80%             perf  [kernel]                        [k] __lock_acquire
                       __lock_acquire
                         lock_acquire
                       |
                       |--58.33%-- _spin_lock
                       |          |
                       |          |--28.57%-- inotify_should_send_event
                       |          |          fsnotify
                      [..]       [..]

   After:

     0.80%             perf  [kernel]                         [k] __lock_acquire
                       |
                       --- __lock_acquire
                           lock_acquire
                          |
                          |--58.33%-- _spin_lock
                          |          |
                          |          |--28.57%-- inotify_should_send_event
                          |          |          fsnotify
                         [..]       [..]

- Otherwise, if we have several top level ancestors, then
  display these like we did before:

       1.69%           Xorg
                       |
                       |--21.21%-- vread_hpet
                       |          0x7fffd85b46fc
                       |          0x7fffd85b494d
                       |          0x7f4fafb4e54d
                       |
                       |--15.15%-- exaOffscreenAlloc
                       |
                       |--9.09%-- I830WaitLpRing
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
LKML-Reference: <1256246604-17156-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>