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Subject[RFC][PATCH 4/8] mm/vmscan: add page demotion counter
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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/migrate.c | 13 ++++++++++++-
b/mm/vmscan.c | 1 +
b/mm/vmstat.c | 2 ++
4 files changed, 17 insertions(+), 1 deletion(-)

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 2020-06-29 16:34:40.332312601 -0700
+++ b/include/linux/vm_event_item.h 2020-06-29 16:34:40.342312601 -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/migrate.c~mm-vmscan-add-page-demotion-counter mm/migrate.c
--- a/mm/migrate.c~mm-vmscan-add-page-demotion-counter 2020-06-29 16:34:40.334312601 -0700
+++ b/mm/migrate.c 2020-06-29 16:34:40.343312601 -0700
@@ -1187,6 +1187,7 @@ static struct page *alloc_demote_node_pa
int migrate_demote_mapping(struct page *page)
{
int next_nid = next_demotion_node(page_to_nid(page));
+ int ret;

VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageHuge(page), page);
@@ -1198,8 +1199,18 @@ int migrate_demote_mapping(struct page *
return -ENOMEM;

/* MIGRATE_ASYNC is the most light weight and never blocks.*/
- return __unmap_and_move(alloc_demote_node_page, NULL, next_nid,
+ ret = __unmap_and_move(alloc_demote_node_page, NULL, next_nid,
page, MIGRATE_ASYNC, MR_DEMOTION);
+
+ if (ret == MIGRATEPAGE_SUCCESS) {
+ int nr_demoted = hpage_nr_pages(page);
+ if (current_is_kswapd())
+ __count_vm_events(PGDEMOTE_KSWAPD, nr_demoted);
+ else
+ __count_vm_events(PGDEMOTE_DIRECT, nr_demoted);
+ }
+
+ return ret;
}


diff -puN mm/vmscan.c~mm-vmscan-add-page-demotion-counter mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-add-page-demotion-counter 2020-06-29 16:34:40.336312601 -0700
+++ b/mm/vmscan.c 2020-06-29 16:34:40.344312601 -0700
@@ -140,6 +140,7 @@ struct scan_control {
unsigned int immediate;
unsigned int file_taken;
unsigned int taken;
+ unsigned int demoted;
} nr;

/* for recording the reclaimed slab by now */
diff -puN mm/vmstat.c~mm-vmscan-add-page-demotion-counter mm/vmstat.c
--- a/mm/vmstat.c~mm-vmscan-add-page-demotion-counter 2020-06-29 16:34:40.339312601 -0700
+++ b/mm/vmstat.c 2020-06-29 16:34:40.345312601 -0700
@@ -1198,6 +1198,8 @@ const char * const vmstat_text[] = {
"pgrefill",
"pgsteal_kswapd",
"pgsteal_direct",
+ "pgdemote_kswapd",
+ "pgdemote_direct",
"pgscan_kswapd",
"pgscan_direct",
"pgscan_direct_throttle",
_
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