[PATCH 8/9] Revert "mm, vmscan: account for skipped pages as a partial scan"

From: Johannes Weiner
Date: Tue Feb 28 2017 - 19:03:45 EST


This reverts commit d7f05528eedb047efe2288cff777676b028747b6.

Now that reclaimability of a node is no longer based on the ratio
between pages scanned and theoretically reclaimable pages, we can
remove accounting tricks for pages skipped due to zone constraints.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
mm/vmscan.c | 22 ++++------------------
1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 35b791a8922b..ddcff8a11c1e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1471,12 +1471,12 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
unsigned long nr_taken = 0;
unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
- unsigned long skipped = 0, total_skipped = 0;
+ unsigned long skipped = 0;
unsigned long scan, nr_pages;
LIST_HEAD(pages_skipped);

for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan &&
- !list_empty(src);) {
+ !list_empty(src); scan++) {
struct page *page;

page = lru_to_page(src);
@@ -1490,12 +1490,6 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
continue;
}

- /*
- * Account for scanned and skipped separetly to avoid the pgdat
- * being prematurely marked unreclaimable by pgdat_reclaimable.
- */
- scan++;
-
switch (__isolate_lru_page(page, mode)) {
case 0:
nr_pages = hpage_nr_pages(page);
@@ -1524,6 +1518,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
if (!list_empty(&pages_skipped)) {
int zid;

+ list_splice(&pages_skipped, src);
for (zid = 0; zid < MAX_NR_ZONES; zid++) {
if (!nr_skipped[zid])
continue;
@@ -1531,17 +1526,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
__count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
skipped += nr_skipped[zid];
}
-
- /*
- * Account skipped pages as a partial scan as the pgdat may be
- * close to unreclaimable. If the LRU list is empty, account
- * skipped pages as a full scan.
- */
- total_skipped = list_empty(src) ? skipped : skipped >> 2;
-
- list_splice(&pages_skipped, src);
}
- *nr_scanned = scan + total_skipped;
+ *nr_scanned = scan;
trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
scan, skipped, nr_taken, mode, lru);
update_lru_sizes(lruvec, lru, nr_zone_taken);
--
2.11.1