[PATCH] mm: remove '!root_reclaim' checking in should_abort_scan()

["zhaoyang.huang" <zhaoyang.huang@unisoc.com>]

From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

Nowadays, ANDROID system replaces madivse with memory.reclaim to implement
user space memory management which desires to reclaim a certain amount of
memcg's memory. However, oversized reclaiming and high latency are observed
as there is no limitation over nr_reclaimed inside try_to_shrink_lruvec
when MGLRU enabled. Besides, this could also affect all none root_reclaim
such as reclaim_high etc.
Since the commit 'b82b530740b9' ("mm: vmscan: restore incremental cgroup
iteration") introduces sc->memcg_full_walk to limit the walk range of
mem_cgroup_iter and keep the fairness among the descendants of one memcg.
This commit would like to make single memcg's scanning more precised by
removing the criteria of 'if (!root_reclaim)' inside
should_abort_scan().

Suggested-by: T.J.Mercier <tjmercier@google.com>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 mm/vmscan.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 670fe9fae5ba..9d900be478ea 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4832,10 +4832,6 @@ static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
 	int i;
 	enum zone_watermarks mark;
 
-	/* don't abort memcg reclaim to ensure fairness */
-	if (!root_reclaim(sc))
-		return false;
-
 	if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order)))
 		return true;
 
-- 
2.25.1