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Tue, 01 Aug 2023 17:19:47 -0700 (PDT) Date: Tue, 1 Aug 2023 17:19:35 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.41.0.255.g8b1d071c50-goog Message-ID: <20230802001938.3913174-1-kaleshsingh@google.com> Subject: [PATCH 1/3] mm-unstable: Multi-gen LRU: Fix per-zone reclaim From: Kalesh Singh To: yuzhao@google.com, akpm@linux-foundation.org Cc: surenb@google.com, android-mm@google.com, kernel-team@android.com, Kalesh Singh , Charan Teja Kalla , Lecopzer Chen , Matthias Brugger , AngeloGioacchino Del Regno , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: AED9A180010 X-Stat-Signature: n3hwu7s5n35ype5imndikj4x97r6zheb X-Rspam-User: X-HE-Tag: 1690935588-499924 X-HE-Meta: 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 Y22s+nDl 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.012603, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Cc: Yu Zhao Cc: Andrew Morton Reported-by: Charan Teja Kalla Reported-by: Lecopzer Chen Signed-off-by: Kalesh Singh --- mm/vmscan.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 4039620d30fe..489a4fc7d9b1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4889,7 +4889,8 @@ static int lru_gen_memcg_seg(struct lruvec *lruvec) * the eviction ******************************************************************************/ -static bool sort_folio(struct lruvec *lruvec, struct folio *folio, int tier_idx) +static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc, + int tier_idx) { bool success; int gen = folio_lru_gen(folio); @@ -4939,6 +4940,13 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, int tier_idx) return true; } + /* ineligible */ + if (zone > sc->reclaim_idx) { + gen = folio_inc_gen(lruvec, folio, false); + list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]); + return true; + } + /* waiting for writeback */ if (folio_test_locked(folio) || folio_test_writeback(folio) || (type == LRU_GEN_FILE && folio_test_dirty(folio))) { @@ -4987,7 +4995,8 @@ static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct sca static int scan_folios(struct lruvec *lruvec, struct scan_control *sc, int type, int tier, struct list_head *list) { - int gen, zone; + int i; + int gen; enum vm_event_item item; int sorted = 0; int scanned = 0; @@ -5003,9 +5012,10 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc, gen = lru_gen_from_seq(lrugen->min_seq[type]); - for (zone = sc->reclaim_idx; zone >= 0; zone--) { + for (i = MAX_NR_ZONES; i > 0; i--) { LIST_HEAD(moved); int skipped = 0; + int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES; struct list_head *head = &lrugen->folios[gen][type][zone]; while (!list_empty(head)) { @@ -5019,7 +5029,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc, scanned += delta; - if (sort_folio(lruvec, folio, tier)) + if (sort_folio(lruvec, folio, sc, tier)) sorted += delta; else if (isolate_folio(lruvec, folio, sc)) { list_add(&folio->lru, list);