tag 0764305435326734127669b6ec80f8d4865d57d1
tagger Deyao Ren <deyaoren@google.com> Wed Aug 09 18:42:20 2023 +0000
object 00ff53e1e06236335c32a14a7bcb87ea5ce2cc0d

android14-6.1 June 2023 release 4

Artifacts:
  https://ci.android.com/builds/submitted/10632443/kernel_aarch64/latest

commit 00ff53e1e06236335c32a14a7bcb87ea5ce2cc0d
author Kalesh Singh <kaleshsingh@google.com> Tue Aug 01 19:56:02 2023 -0700
committer Kalesh Singh <kaleshsingh@google.com> Wed Aug 09 03:11:15 2023 +0000
tree bda27eafeb674c26aac78ab0d5148e67e2d76610
parent 886f4b317ef198a14020e218b2f78cdc9b963b24

FROMGIT: Multi-gen LRU: Fix per-zone reclaim

MGLRU has a LRU list for each zone for each type (anon/file) in each
generation:

	long nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES];

The min_seq (oldest generation) can progress independently for each
type but the max_seq (youngest generation) is shared for both anon and
file. This is to maintain a common frame of reference.

In order for eviction to advance the min_seq of a type, all the per-zone
lists in the oldest generation of that type must be empty.

The eviction logic only considers pages from eligible zones for
eviction or promotion.

    scan_folios() {
	...
	for (zone = sc->reclaim_idx; zone >= 0; zone--)  {
	    ...
	    sort_folio(); 	// Promote
	    ...
	    isolate_folio(); 	// Evict
	}
	...
    }

Consider the system has the movable zone configured and default 4
generations. The current state of the system is as shown below
(only illustrating one type for simplicity):

Type: ANON

	Zone    DMA32     Normal    Movable    Device

	Gen 0       0          0        4GB         0

	Gen 1       0        1GB        1MB         0

	Gen 2     1MB        4GB        1MB         0

	Gen 3     1MB        1MB        1MB         0

Now consider there is a GFP_KERNEL allocation request (eligible zone
index <= Normal), evict_folios() will return without doing any work
since there are no pages to scan in the eligible zones of the oldest
generation. Reclaim won't make progress until triggered from a ZONE_MOVABLE
allocation request; which may not happen soon if there is a lot of free
memory in the movable zone. This can lead to OOM kills, although there
is 1GB pages in the Normal zone of Gen 1 that we have not yet tried to
reclaim.

This issue is not seen in the conventional active/inactive LRU since
there are no per-zone lists.

If there are no (not enough) folios to scan in the eligible zones, move
folios from ineligible zone (zone_index > reclaim_index) to the next
generation. This allows for the progression of min_seq and reclaiming
from the next generation (Gen 1).

Qualcomm, Mediatek and raspberrypi [1] discovered this issue independently.

[1] https://github.com/raspberrypi/linux/issues/5395

Link: https://lkml.kernel.org/r/20230802025606.346758-1-kaleshsingh@google.com
Fixes: ac35a4902374 ("mm: multi-gen LRU: minimal implementation")
Change-Id: I5bbf44bd7ffe42f4347df4be59a75c1603c9b947
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reported-by: Charan Teja Kalla <quic_charante@quicinc.com>
Reported-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> [mediatek]
Tested-by: Charan Teja Kalla <quic_charante@quicinc.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Steven Barrett <steven@liquorix.net>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 1462260adc41c5974362cb54ff577c2a15b8c7b2 https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable)
Bug: 295078665
Bug: 288383787
Bug: 291719697
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
(cherry picked from commit a7adb988970e13c42f3c7ca4fe157c35e8e885fe)