kernel: Update MGLRU patchset

The current patches are old, update them from mainline.
Backports taken from https://github.com/yuzhaogoogle/linux/commits/mglru-5.15

Tested-by: Kazuki H <kazukih0205@gmail.com> #mt7622/Linksys E8450 UBI
Signed-off-by: Kazuki H <kazukih0205@gmail.com>

1 files changed, 193 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.15/020-v6.3-23-mm-multi-gen-LRU-remove-eviction-fairness-safeguard.patch b/target/linux/generic/backport-5.15/020-v6.3-23-mm-multi-gen-LRU-remove-eviction-fairness-safeguard.patch
new file mode 100644
index 0000000000..1490f9d4bc
--- /dev/null
+++ b/target/linux/generic/backport-5.15/020-v6.3-23-mm-multi-gen-LRU-remove-eviction-fairness-safeguard.patch
@@ -0,0 +1,193 @@
+From ce45f1c4b32cf69b166f56ef5bc6c761e06ed4e5 Mon Sep 17 00:00:00 2001
+From: Yu Zhao <yuzhao@google.com>
+Date: Wed, 21 Dec 2022 21:19:01 -0700
+Subject: [PATCH 23/29] mm: multi-gen LRU: remove eviction fairness safeguard
+
+Recall that the eviction consumes the oldest generation: first it
+bucket-sorts pages whose gen counters were updated by the aging and
+reclaims the rest; then it increments lrugen->min_seq.
+
+The current eviction fairness safeguard for global reclaim has a
+dilemma: when there are multiple eligible memcgs, should it continue
+or stop upon meeting the reclaim goal? If it continues, it overshoots
+and increases direct reclaim latency; if it stops, it loses fairness
+between memcgs it has taken memory away from and those it has yet to.
+
+With memcg LRU, the eviction, while ensuring eventual fairness, will
+stop upon meeting its goal. Therefore the current eviction fairness
+safeguard for global reclaim will not be needed.
+
+Note that memcg LRU only applies to global reclaim. For memcg reclaim,
+the eviction will continue, even if it is overshooting. This becomes
+unconditional due to code simplification.
+
+Link: https://lkml.kernel.org/r/20221222041905.2431096-4-yuzhao@google.com
+Signed-off-by: Yu Zhao <yuzhao@google.com>
+Cc: Johannes Weiner <hannes@cmpxchg.org>
+Cc: Jonathan Corbet <corbet@lwn.net>
+Cc: Michael Larabel <Michael@MichaelLarabel.com>
+Cc: Michal Hocko <mhocko@kernel.org>
+Cc: Mike Rapoport <rppt@kernel.org>
+Cc: Roman Gushchin <roman.gushchin@linux.dev>
+Cc: Suren Baghdasaryan <surenb@google.com>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+---
+ mm/vmscan.c | 82 +++++++++++++++--------------------------------------
+ 1 file changed, 23 insertions(+), 59 deletions(-)
+
+diff --git a/mm/vmscan.c b/mm/vmscan.c
+index 2322c913aa64..40e7a947c5c7 100644
+--- a/mm/vmscan.c
++++ b/mm/vmscan.c
+@@ -443,6 +443,11 @@ static bool cgroup_reclaim(struct scan_control *sc)
+ 	return sc->target_mem_cgroup;
+ }
+ 
++static bool global_reclaim(struct scan_control *sc)
++{
++	return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup);
++}
++
+ /**
+  * writeback_throttling_sane - is the usual dirty throttling mechanism available?
+  * @sc: scan_control in question
+@@ -493,6 +498,11 @@ static bool cgroup_reclaim(struct scan_control *sc)
+ 	return false;
+ }
+ 
++static bool global_reclaim(struct scan_control *sc)
++{
++	return true;
++}
++
+ static bool writeback_throttling_sane(struct scan_control *sc)
+ {
+ 	return true;
+@@ -4722,8 +4732,7 @@ static int isolate_pages(struct lruvec *lruvec, struct scan_control *sc, int swa
+ 	return scanned;
+ }
+ 
+-static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
+-		       bool *need_swapping)
++static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swappiness)
+ {
+ 	int type;
+ 	int scanned;
+@@ -4812,9 +4821,6 @@ static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swapp
+ 		goto retry;
+ 	}
+ 
+-	if (need_swapping && type == LRU_GEN_ANON)
+-		*need_swapping = true;
+-
+ 	return scanned;
+ }
+ 
+@@ -4853,68 +4859,26 @@ static unsigned long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *
+ 	return min_seq[!can_swap] + MIN_NR_GENS <= max_seq ? nr_to_scan : 0;
+ }
+ 
+-static bool should_abort_scan(struct lruvec *lruvec, unsigned long seq,
+-			      struct scan_control *sc, bool need_swapping)
++static unsigned long get_nr_to_reclaim(struct scan_control *sc)
+ {
+-	int i;
+-	DEFINE_MAX_SEQ(lruvec);
+-
+-	if (!current_is_kswapd()) {
+-		/* age each memcg once to ensure fairness */
+-		if (max_seq - seq > 1)
+-			return true;
+-
+-		/* over-swapping can increase allocation latency */
+-		if (sc->nr_reclaimed >= sc->nr_to_reclaim && need_swapping)
+-			return true;
+-
+-		/* give this thread a chance to exit and free its memory */
+-		if (fatal_signal_pending(current)) {
+-			sc->nr_reclaimed += MIN_LRU_BATCH;
+-			return true;
+-		}
+-
+-		if (cgroup_reclaim(sc))
+-			return false;
+-	} else if (sc->nr_reclaimed - sc->last_reclaimed < sc->nr_to_reclaim)
+-		return false;
+-
+-	/* keep scanning at low priorities to ensure fairness */
+-	if (sc->priority > DEF_PRIORITY - 2)
+-		return false;
+-
+-	/*
+-	 * A minimum amount of work was done under global memory pressure. For
+-	 * kswapd, it may be overshooting. For direct reclaim, the target isn't
+-	 * met, and yet the allocation may still succeed, since kswapd may have
+-	 * caught up. In either case, it's better to stop now, and restart if
+-	 * necessary.
+-	 */
+-	for (i = 0; i <= sc->reclaim_idx; i++) {
+-		unsigned long wmark;
+-		struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i;
+-
+-		if (!managed_zone(zone))
+-			continue;
+-
+-		wmark = current_is_kswapd() ? high_wmark_pages(zone) : low_wmark_pages(zone);
+-		if (wmark > zone_page_state(zone, NR_FREE_PAGES))
+-			return false;
+-	}
++	/* don't abort memcg reclaim to ensure fairness */
++	if (!global_reclaim(sc))
++		return -1;
+ 
+-	sc->nr_reclaimed += MIN_LRU_BATCH;
++	/* discount the previous progress for kswapd */
++	if (current_is_kswapd())
++		return sc->nr_to_reclaim + sc->last_reclaimed;
+ 
+-	return true;
++	return max(sc->nr_to_reclaim, compact_gap(sc->order));
+ }
+ 
+ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+ {
+ 	struct blk_plug plug;
+ 	bool need_aging = false;
+-	bool need_swapping = false;
+ 	unsigned long scanned = 0;
+ 	unsigned long reclaimed = sc->nr_reclaimed;
+-	DEFINE_MAX_SEQ(lruvec);
++	unsigned long nr_to_reclaim = get_nr_to_reclaim(sc);
+ 
+ 	lru_add_drain();
+ 
+@@ -4938,7 +4902,7 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
+ 		if (!nr_to_scan)
+ 			goto done;
+ 
+-		delta = evict_pages(lruvec, sc, swappiness, &need_swapping);
++		delta = evict_pages(lruvec, sc, swappiness);
+ 		if (!delta)
+ 			goto done;
+ 
+@@ -4946,7 +4910,7 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
+ 		if (scanned >= nr_to_scan)
+ 			break;
+ 
+-		if (should_abort_scan(lruvec, max_seq, sc, need_swapping))
++		if (sc->nr_reclaimed >= nr_to_reclaim)
+ 			break;
+ 
+ 		cond_resched();
+@@ -5393,7 +5357,7 @@ static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_co
+ 		if (sc->nr_reclaimed >= nr_to_reclaim)
+ 			return 0;
+ 
+-		if (!evict_pages(lruvec, sc, swappiness, NULL))
++		if (!evict_pages(lruvec, sc, swappiness))
+ 			return 0;
+ 
+ 		cond_resched();
+-- 
+2.40.0
+