perf kmem: Support sort keys on page analysis

Add new sort keys for page: page, order, migtype, gfp - existing
'bytes', 'hit' and 'callsite' sort keys also work for page.  Note that
-s/--sort option should be preceded by either of --slab or --page option
to determine where the sort keys applies.

Now it properly groups and sorts allocation stats - so same
page/caller with different order/migtype/gfp will be printed on a
different line.

 # perf kmem stat --page --caller -l 10 -s order,hit

 -----------------------------------------------------------------------------
 Total alloc (KB) | Hits   | Order | Mig.type | GFP flags | Callsite
 -----------------------------------------------------------------------------
               64 |      4 |     2 |  RECLAIM |  00285250 | new_slab
           50,144 | 12,536 |     0 |  MOVABLE |  0102005a | __page_cache_alloc
               52 |     13 |     0 | UNMOVABL |  002084d0 | pte_alloc_one
               40 |     10 |     0 |  MOVABLE |  000280da | handle_mm_fault
               28 |      7 |     0 | UNMOVABL |  000000d0 | __pollwait
               20 |      5 |     0 |  MOVABLE |  000200da | do_wp_page
               20 |      5 |     0 |  MOVABLE |  000200da | do_cow_fault
               16 |      4 |     0 | UNMOVABL |  00000200 | __tlb_remove_page
               16 |      4 |     0 | UNMOVABL |  000084d0 | __pmd_alloc
                8 |      2 |     0 | UNMOVABL |  000084d0 | __pud_alloc
 ...              | ...    | ...   | ...      | ...       | ...
 -----------------------------------------------------------------------------

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1429592107-1807-3-git-send-email-namhyung@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>