linux-kernel - [PATCH 2/2] mm, vmstat: List total free blocks for each order in /proc/pagetypeinfo

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Date:   Wed, 23 Oct 2019 13:34:23 -0400
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>, Mel Gorman <mgorman@...e.de>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Vlastimil Babka <vbabka@...e.cz>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jann Horn <jannh@...gle.com>, Song Liu <songliubraving@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rafael Aquini <aquini@...hat.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH 2/2] mm, vmstat: List total free blocks for each order in /proc/pagetypeinfo

Now that the free block count for each migration types in
/proc/pagetypeinfo may not show the exact count if it excceeds
100,000. Users may not know how much more the counts will be. As the
free_area structure has already tracked the total free block count in
nr_free, we may as well print it out with no additional cost. That will
give users a rough idea of where the upper bounds will be.

If there is no overflow, the presence of the total counts will also
enable us to check if the nr_free counts match the total number of
entries in the free lists.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 mm/vmstat.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index c5b82fdf54af..172946d8f358 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1373,6 +1373,7 @@ static void pagetypeinfo_showfree_print(struct seq_file *m,
 					pg_data_t *pgdat, struct zone *zone)
 {
 	int order, mtype;
+	struct free_area *area;
 	unsigned long iteration_count = 0;
 
 	for (mtype = 0; mtype < MIGRATE_TYPES; mtype++) {
@@ -1382,7 +1383,6 @@ static void pagetypeinfo_showfree_print(struct seq_file *m,
 					migratetype_names[mtype]);
 		for (order = 0; order < MAX_ORDER; ++order) {
 			unsigned long freecount = 0;
-			struct free_area *area;
 			struct list_head *curr;
 			bool overflow = false;
 
@@ -1419,6 +1419,17 @@ static void pagetypeinfo_showfree_print(struct seq_file *m,
 		}
 		seq_putc(m, '\n');
 	}
+
+	/*
+	 * List total free blocks per order
+	 */
+	seq_printf(m, "Node %4d, zone %8s, total             ",
+		   pgdat->node_id, zone->name);
+	for (order = 0; order < MAX_ORDER; ++order) {
+		area = &(zone->free_area[order]);
+		seq_printf(m, "%6lu ", area->nr_free);
+	}
+	seq_putc(m, '\n');
 }
 
 /* Print out the free pages at each order for each migatetype */
-- 
2.18.1