[cachetop] Display sorting field and order.

This will make it easier to visualize what is the sorting field
and order

tools/cachetop.py

@@ -213,8 +213,10 @@ def handle_loop(stdscr, args):
  stdscr.clear()
  stdscr.addstr(
  0, 0,
- "%-8s Buffers MB: %.0f / Cached MB: %.0f" % (
- strftime("%H:%M:%S"), buff, cached
+ "%-8s Buffers MB: %.0f / Cached MB: %.0f "
+ "/ Sort: %s / Order: %s" % (
+ strftime("%H:%M:%S"), buff, cached, FIELDS[sort_field],
+ sort_reverse and "descending" or "ascending"
  )
  )
 

tools/cachetop_example.txt

@@ -15,7 +15,7 @@ examples:
  ./cachetop 1 # print every second hit/miss stats
 
 # ./cachetop 5
-13:01:01 Buffers MB: 76 / Cached MB: 114
+13:01:01 Buffers MB: 76 / Cached MB: 114 / Sort: HITS / Order: ascending
 PID UID CMD HITS MISSES DIRTIES READ_HIT% WRITE_HIT%
  1 root systemd 2 0 0 100.0% 0.0%
  680 root vminfo 3 4 2 14.3% 42.9%
@@ -43,7 +43,7 @@ Command used to generate the activity
 Below shows the hit rate increases as we run find a second time and it gets it
 its pages from the cache.
 # ./cachetop.py
-13:01:01 Buffers MB: 76 / Cached MB: 115
+13:01:01 Buffers MB: 76 / Cached MB: 115 / Sort: HITS / Order: ascending
 PID UID CMD HITS MISSES DIRTIES READ_HIT% WRITE_HIT%
  544 messageb dbus-daemon 2 2 1 25.0% 50.0%
  680 root vminfo 2 2 1 25.0% 50.0%
@@ -57,7 +57,7 @@ Below shows that the dirty pages increases as a file of 80M is created running
 # dd if=/dev/urandom of=/tmp/c bs=8192 count=10000
 
 # ./cachetop.py 10
-13:01:01 Buffers MB: 77 / Cached MB: 193
+13:01:01 Buffers MB: 77 / Cached MB: 193 / Sort: HITS / Order: ascending
 PID UID CMD HITS MISSES DIRTIES READ_HIT% WRITE_HIT%
  544 messageb dbus-daemon 9 10 7 10.5% 15.8%
  680 root vminfo 9 10 7 10.5% 15.8%