vmscan: add a vmscan event for reclaim_pages

reclaim_folio_list uses a dummy reclaim_stat and is not being used.  To
know the memory stat, add a new trace event.  This is useful how how many
pages are not reclaimed or why.

This is an example:

mm_vmscan_reclaim_pages: nid=0 nr_scanned=112 nr_reclaimed=112 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0

Currently reclaim_folio_list is only called by reclaim_pages, and
reclaim_pages is used by damon and madvise.  In the latest Android,
reclaim_pages is also used by shmem to reclaim all pages in a
address_space.

[[email protected]: use sc.nr_scanned rather than new counting]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jaewon Kim <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Jaewon Kim <[email protected]>
Cc: Kalesh Singh <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: SeongJae Park <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions