mm, THP, swap: add THP swapping out fallback counting
When swapping out THP (Transparent Huge Page), instead of swapping out
the THP as a whole, sometimes we have to fallback to split the THP into
normal pages before swapping, because no free swap clusters are
available, or cgroup limit is exceeded, etc. To count the number of the
fallback, a new VM event THP_SWPOUT_FALLBACK is added, and counted when
we fallback to split the THP.
Link: http://lkml.kernel.org/r/20170724051840.2309-13-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c]
Cc: Vishal L Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index c75024e..e02820f 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -86,6 +86,7 @@
THP_ZERO_PAGE_ALLOC,
THP_ZERO_PAGE_ALLOC_FAILED,
THP_SWPOUT,
+ THP_SWPOUT_FALLBACK,
#endif
#ifdef CONFIG_MEMORY_BALLOON
BALLOON_INFLATE,
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6fbf707..13d711d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1154,6 +1154,9 @@
if (split_huge_page_to_list(page,
page_list))
goto activate_locked;
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ count_vm_event(THP_SWPOUT_FALLBACK);
+#endif
if (!add_to_swap(page))
goto activate_locked;
}
diff --git a/mm/vmstat.c b/mm/vmstat.c
index bccf426..e131b51 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1072,6 +1072,7 @@
"thp_zero_page_alloc",
"thp_zero_page_alloc_failed",
"thp_swpout",
+ "thp_swpout_fallback",
#endif
#ifdef CONFIG_MEMORY_BALLOON
"balloon_inflate",