linux-kernel - [RFC][PATCH 6/9] mm/vmscan: add page demotion counter

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Message-Id: <20201007161747.FE7288F0@viggo.jf.intel.com>
Date:   Wed, 07 Oct 2020 09:17:47 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        yang.shi@...ux.alibaba.com, rientjes@...gle.com,
        ying.huang@...el.com, dan.j.williams@...el.com, david@...hat.com
Subject: [RFC][PATCH 6/9] mm/vmscan: add page demotion counter


From: Yang Shi <yang.shi@...ux.alibaba.com>

Account the number of demoted pages into reclaim_state->nr_demoted.

Add pgdemote_kswapd and pgdemote_direct VM counters showed in
/proc/vmstat.

[ daveh:
   - __count_vm_events() a bit, and made them look at the THP
     size directly rather than getting data from migrate_pages()
]

Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: David Hildenbrand <david@...hat.com>
---

 b/include/linux/vm_event_item.h |    2 ++
 b/mm/vmscan.c                   |    6 ++++++
 b/mm/vmstat.c                   |    2 ++
 3 files changed, 10 insertions(+)

diff -puN include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter include/linux/vm_event_item.h
--- a/include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter	2020-10-07 09:15:32.171642439 -0700
+++ b/include/linux/vm_event_item.h	2020-10-07 09:15:32.179642439 -0700
@@ -33,6 +33,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
 		PGREUSE,
 		PGSTEAL_KSWAPD,
 		PGSTEAL_DIRECT,
+		PGDEMOTE_KSWAPD,
+		PGDEMOTE_DIRECT,
 		PGSCAN_KSWAPD,
 		PGSCAN_DIRECT,
 		PGSCAN_DIRECT_THROTTLE,
diff -puN mm/vmscan.c~mm-vmscan-add-page-demotion-counter mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-add-page-demotion-counter	2020-10-07 09:15:32.173642439 -0700
+++ b/mm/vmscan.c	2020-10-07 09:15:32.180642439 -0700
@@ -147,6 +147,7 @@ struct scan_control {
 		unsigned int immediate;
 		unsigned int file_taken;
 		unsigned int taken;
+		unsigned int demoted;
 	} nr;
 
 	/* for recording the reclaimed slab by now */
@@ -1134,6 +1135,11 @@ static unsigned int demote_page_list(str
 			    target_nid, MIGRATE_ASYNC, MR_DEMOTION,
 			    &nr_succeeded);
 
+	if (current_is_kswapd())
+		__count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
+	else
+		__count_vm_events(PGDEMOTE_DIRECT, nr_succeeded);
+
 	return nr_succeeded;
 }
 
diff -puN mm/vmstat.c~mm-vmscan-add-page-demotion-counter mm/vmstat.c
--- a/mm/vmstat.c~mm-vmscan-add-page-demotion-counter	2020-10-07 09:15:32.175642439 -0700
+++ b/mm/vmstat.c	2020-10-07 09:15:32.181642439 -0700
@@ -1244,6 +1244,8 @@ const char * const vmstat_text[] = {
 	"pgreuse",
 	"pgsteal_kswapd",
 	"pgsteal_direct",
+	"pgdemote_kswapd",
+	"pgdemote_direct",
 	"pgscan_kswapd",
 	"pgscan_direct",
 	"pgscan_direct_throttle",
_