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Subject: [RFC][PATCH 6/9] mm/vmscan: add page demotion counter
To:     linux-kernel@vger.kernel.org
Cc:     Dave Hansen <dave.hansen@linux.intel.com>,
        yang.shi@linux.alibaba.com, rientjes@google.com,
        ying.huang@intel.com, dan.j.williams@intel.com
From:   Dave Hansen <dave.hansen@linux.intel.com>
Date:   Tue, 18 Aug 2020 11:41:33 -0700
References: <20200818184122.29C415DF@viggo.jf.intel.com>
In-Reply-To: <20200818184122.29C415DF@viggo.jf.intel.com>
Message-Id: <20200818184133.DCF58B5F@viggo.jf.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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From: Yang Shi <yang.shi@linux.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@linux.alibaba.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.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	2020-08-18 11:36:54.062583176 -0700
+++ b/include/linux/vm_event_item.h	2020-08-18 11:36:54.070583176 -0700
@@ -32,6 +32,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
 		PGREFILL,
 		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	2020-08-18 11:36:54.064583176 -0700
+++ b/mm/vmscan.c	2020-08-18 11:36:54.072583176 -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 */
@@ -1146,6 +1147,11 @@ static unsigned int demote_page_list(str
 		list_splice(ret_list, demote_pages);
 	}
 
+	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	2020-08-18 11:36:54.067583176 -0700
+++ b/mm/vmstat.c	2020-08-18 11:36:54.072583176 -0700
@@ -1200,6 +1200,8 @@ const char * const vmstat_text[] = {
 	"pgrefill",
 	"pgsteal_kswapd",
 	"pgsteal_direct",
+	"pgdemote_kswapd",
+	"pgdemote_direct",
 	"pgscan_kswapd",
 	"pgscan_direct",
 	"pgscan_direct_throttle",
_