Commit f934393a authored by Yu Zhao's avatar Yu Zhao Committed by Peng Zhang
Browse files

mm/mglru: reclaim offlined memcgs harder 

stable inclusion
from stable-v6.6.8
commit a107d6a132cbb596afa648f588f0078713ad46e9
bugzilla: https://gitee.com/openeuler/kernel/issues/I99K53

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a107d6a132cbb596afa648f588f0078713ad46e9

--------------------------------

commit 4376807bf2d5371c3e00080c972be568c3f8a7d1 upstream.

In the effort to reduce zombie memcgs [1], it was discovered that the
memcg LRU doesn't apply enough pressure on offlined memcgs.  Specifically,
instead of rotating them to the tail of the current generation
(MEMCG_LRU_TAIL) for a second attempt, it moves them to the next
generation (MEMCG_LRU_YOUNG) after the first attempt.

Not applying enough pressure on offlined memcgs can cause them to build
up, and this can be particularly harmful to memory-constrained systems.

On Pixel 8 Pro, launching apps for 50 cycles:
                 Before  After  Change
  Zombie memcgs  45      35     -22%

[1] https://lore.kernel.org/CABdmKX2M6koq4Q0Cmp_-=wbP0Qa190HdEGGaHfxNS05gAkUtPA@mail.gmail.com/

Link: https://lkml.kernel.org/r/20231208061407.2125867-4-yuzhao@google.com


Fixes: e4dde56c ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: default avatarYu Zhao <yuzhao@google.com>
Reported-by: default avatarT.J. Mercier <tjmercier@google.com>
Tested-by: default avatarT.J. Mercier <tjmercier@google.com>
Cc: Charan Teja Kalla <quic_charante@quicinc.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Jaroslav Pulchart <jaroslav.pulchart@gooddata.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarZhangPeng <zhangpeng362@huawei.com>
parent 1f1ef9e7

include/linux/mmzone.h

+4 −4
Original line number Diff line number Diff line
@@ -528,10 +528,10 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw); 
 * 1. Exceeding the soft limit, which triggers MEMCG_LRU_HEAD;

 * 2. The first attempt to reclaim a memcg below low, which triggers

 *    MEMCG_LRU_TAIL;

 * 3. The first attempt to reclaim a memcg below reclaimable size threshold,

 *    which triggers MEMCG_LRU_TAIL;

 * 4. The second attempt to reclaim a memcg below reclaimable size threshold,

 *    which triggers MEMCG_LRU_YOUNG;

 * 3. The first attempt to reclaim a memcg offlined or below reclaimable size

 *    threshold, which triggers MEMCG_LRU_TAIL;

 * 4. The second attempt to reclaim a memcg offlined or below reclaimable size

 *    threshold, which triggers MEMCG_LRU_YOUNG;

 * 5. Attempting to reclaim a memcg below min, which triggers MEMCG_LRU_YOUNG;

 * 6. Finishing the aging on the eviction path, which triggers MEMCG_LRU_YOUNG;

 * 7. Offlining a memcg, which triggers MEMCG_LRU_OLD.

mm/vmscan.c

+16 −8
Original line number Diff line number Diff line
@@ -5311,7 +5311,12 @@ static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, 
	}



	/* try to scrape all its memory if this memcg was deleted */

	*nr_to_scan = mem_cgroup_online(memcg) ? (total >> sc->priority) : total;

	if (!mem_cgroup_online(memcg)) {

		*nr_to_scan = total;

		return false;

	}



	*nr_to_scan = total >> sc->priority;



	/*

	 * The aging tries to be lazy to reduce the overhead, while the eviction
@@ -5432,14 +5437,9 @@ static int shrink_one(struct lruvec *lruvec, struct scan_control *sc) 
	bool success;

	unsigned long scanned = sc->nr_scanned;

	unsigned long reclaimed = sc->nr_reclaimed;

	int seg = lru_gen_memcg_seg(lruvec);

	struct mem_cgroup *memcg = lruvec_memcg(lruvec);

	struct pglist_data *pgdat = lruvec_pgdat(lruvec);



	/* see the comment on MEMCG_NR_GENS */

	if (!lruvec_is_sizable(lruvec, sc))

		return seg != MEMCG_LRU_TAIL ? MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;



	mem_cgroup_calculate_protection(NULL, memcg);



	if (mem_cgroup_below_min(NULL, memcg))
@@ -5447,7 +5447,7 @@ static int shrink_one(struct lruvec *lruvec, struct scan_control *sc) 


	if (mem_cgroup_below_low(NULL, memcg)) {

		/* see the comment on MEMCG_NR_GENS */

		if (seg != MEMCG_LRU_TAIL)

		if (lru_gen_memcg_seg(lruvec) != MEMCG_LRU_TAIL)

			return MEMCG_LRU_TAIL;



		memcg_memory_event(memcg, MEMCG_LOW);
@@ -5463,7 +5463,15 @@ static int shrink_one(struct lruvec *lruvec, struct scan_control *sc) 


	flush_reclaim_state(sc);



	return success ? MEMCG_LRU_YOUNG : 0;

	if (success && mem_cgroup_online(memcg))

		return MEMCG_LRU_YOUNG;



	if (!success && lruvec_is_sizable(lruvec, sc))

		return 0;



	/* one retry if offlined or too small */

	return lru_gen_memcg_seg(lruvec) != MEMCG_LRU_TAIL ?

	       MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;

}



#ifdef CONFIG_MEMCG