tracing, page-allocator: add a postprocessing script for page-allocator-related ftrace events

This patch adds a simple post-processing script for the
page-allocator-related trace events.  It can be used to give an indication
of who the most allocator-intensive processes are and how often the zone
lock was taken during the tracing period.  Example output looks like

Process                   Pages      Pages      Pages    Pages       PCPU     PCPU     PCPU   Fragment Fragment  MigType Fragment Fragment  Unknown
details                  allocd     allocd      freed    freed      pages   drains  refills   Fallback  Causing  Changed   Severe Moderate
                                under lock     direct  pagevec      drain
swapper-0                     0          0          2        0          0        0        0          0        0        0        0        0        0
Xorg-3770                 10603       5952       3685     6978       5996      194      192          0        0        0        0        0        0
modprobe-21397               51          0          0       86         31        1        0          0        0        0        0        0        0
xchat-5370                  228         93          0        0          0        0        3          0        0        0        0        0        0
awesome-4317                 32         32          0        0          0        0       32          0        0        0        0        0        0
thinkfan-3863                 2          0          1        1          0        0        0          0        0        0        0        0        0
hald-addon-stor-3935          2          0          0        0          0        0        0          0        0        0        0        0        0
akregator-4506                1          1          0        0          0        0        1          0        0        0        0        0        0
xmms-14888                    0          0          1        0          0        0        0          0        0        0        0        0        0
khelper-12                    1          0          0        0          0        0        0          0        0        0        0        0        0

Optionally, the output can include information on the parent or aggregate
based on process name instead of aggregating based on each pid. Example output
including parent information and stripped out the PID looks something like;

Process                        Pages      Pages      Pages    Pages       PCPU     PCPU     PCPU   Fragment Fragment  MigType Fragment Fragment  Unknown
details                       allocd     allocd      freed    freed      pages   drains  refills   Fallback  Causing  Changed   Severe Moderate
                                     under lock     direct  pagevec      drain
gdm-3756 :: Xorg-3770           3796       2976         99     3813       3224      104       98          0        0        0        0        0        0
init-1 :: hald-3892                1          0          0        0          0        0        0          0        0        0        0        0        0
git-21447 :: editor-21448          4          0          4        0          0        0        0          0        0        0        0        0        0

This says that Xorg allocated 3796 pages and it's parent process is gdm
with a PID of 3756;

The postprocessor parses the text output of tracing.  While there is a
binary format, the expectation is that the binary output can be readily
translated into text and post-processed offline.  Obviously if the text
format changes, the parser will break but the regular expression parser is
fairly rudimentary so should be readily adjustable.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Li Ming Chun <macli@brc.ubc.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>