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

[Johannes Weiner]

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 <han...@cmpxchg.org>
---
 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