mm/page_alloc.c: show watermark_boost of zone in zoneinfo

min/low/high_wmark_pages(z) is defined as

  (z->_watermark[WMARK_MIN/LOW/HIGH] + z->watermark_boost)

If kswapd is frequently woken up due to the increase of
min/low/high_wmark_pages, printing watermark_boost can quickly locate
whether watermark_boost or _watermark[WMARK_MIN/LOW/HIGH] caused
min/low/high_wmark_pages to increase.

Link: https://lkml.kernel.org/r/1632472566-12246-1-git-send-email-liangcaifan19@gmail.com
Signed-off-by: Liangcai Fan <liangcaifan19@gmail.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -5993,6 +5993,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 		printk(KERN_CONT
 			"%s"
 			" free:%lukB"
+			" boost:%lukB"
 			" min:%lukB"
 			" low:%lukB"
 			" high:%lukB"
@@ -6013,6 +6014,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 			"\n",
 			zone->name,
 			K(zone_page_state(zone, NR_FREE_PAGES)),
+			K(zone->watermark_boost),
 			K(min_wmark_pages(zone)),
 			K(low_wmark_pages(zone)),
 			K(high_wmark_pages(zone)),

mm/vmstat.c

@@ -1656,6 +1656,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 	}
 	seq_printf(m,
 		   "\n  pages free     %lu"
+		   "\n        boost    %lu"
 		   "\n        min      %lu"
 		   "\n        low      %lu"
 		   "\n        high     %lu"
@@ -1664,6 +1665,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 		   "\n        managed  %lu"
 		   "\n        cma      %lu",
 		   zone_page_state(zone, NR_FREE_PAGES),
+		   zone->watermark_boost,
 		   min_wmark_pages(zone),
 		   low_wmark_pages(zone),
 		   high_wmark_pages(zone),