From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 87273374E67 for ; Sun, 26 Jul 2026 01:30:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785029403; cv=none; b=rvMLt0X+tvtVh/1aUNZpNHmdq73X5w1XaJGSINkdpWHj1zNS/g/6cdkn0POGXiB71a4Ta+iAPNs800wSIDlBRQ/ikY5qLd0W6yj4JGvIc5SR4A1VHZWovsIGDDPhAemrJRHWFlpTi0yom6zQapJp6TYt40yJCYBdrxw2bovV/u0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785029403; c=relaxed/simple; bh=FQIeXKPyYly8fD5qG/FPMm3Yhun2ovE56TyaPZGqzfE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=UuxYcGMHP0jauBTGWfuSatHbqsbICUkwbwboJxf09V40C49pQjYwz2TyaN+egjAexBtsXRGzTNba59X1zgyDM50Q0atxNlOlbK++NdyLqVjBXvw+TD6VdWCFURYZFlh98QHE3cMeafmFirc1rVWzL+Fn2oYUBP5h6Eg9bzrsbyE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=B/c/+WNY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="B/c/+WNY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B3B41F00A3D; Sun, 26 Jul 2026 01:29:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785029402; bh=9jhQTuuPD9KwcoX/z0WxrFRGD97WTuKY5ASJ3vGdEAY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=B/c/+WNYqFuq5bvjJiDUU4Quc1DnVZR4VWTfmaF2VYh+iwj3+SHvs6V3FzzIn9pOx ZL4kZPsoiwy34n9G4rD4Luj9U28lBptb4feHZtkaLaliCIDwisAaaAw6iQQa+gW/wT 3w4/Tgv9gUuITSL9LSw4xGx/V8IALyw+zYoHBVtnE4NldU9UkokKt232OZiWjFBNkP l/ZyEIrGXriUhJviR6u6WWYbjhrBD8gXVcTnWMNBi+k/LMtawyM6cW/U7sQ87n2N9r bijwzqWyxeOgEmmcUePFVzL+703xQwK9zIo7oEIxPssrGjJaYFPe5r7L5mW1IZrTeQ kgTXl+0172iXg== From: "Barry Song (Xiaomi)" To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org, kasong@tencent.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, linux-kernel@vger.kernel.org, lyugaofei@xiaomi.com, stevensd@chromium.org, Barry Song Subject: [RFC PATCH 3/4] mm: mglru: run aging when pages are severely imbalanced across gens Date: Sun, 26 Jul 2026 09:29:45 +0800 Message-Id: <20260726012946.18684-4-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20260726012946.18684-1-baohua@kernel.org> References: <20260726012946.18684-1-baohua@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: lyugaofei This partially restores the reclaim behavior introduced in Yu Zhao's initial MGLRU commit, ac35a4902370 ("mm: multi-gen LRU: minimal implementation"): /* * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1) * of the total number of pages for each generation. A reasonable range * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The * aging cares about the upper bound of hot pages, while the eviction * cares about the lower bound of cold pages. */ if (young * MIN_NR_GENS > total) return true; if (old * (MIN_NR_GENS + 2) < total) return true; But with a stricter condition: the youngest gen must have at least four times as many folios as the oldest. This helps keep folios of the preferred type distributed across the reclaimable gens. Signed-off-by: lyugaofei Co-developed-by: Barry Song (Xiaomi) Signed-off-by: Barry Song (Xiaomi) --- mm/vmscan.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 4f3a375de86e..9aac4febc206 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4963,9 +4963,37 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, return scanned; } +static bool lru_gen_imbalanced(struct lruvec *lruvec, int type, + unsigned long max_seq, unsigned long min_seq, + int swappiness) +{ + struct lru_gen_folio *lrugen = &lruvec->lrugen; + unsigned long young = 0, old = 0, seq; + + if (swappiness == MIN_SWAPPINESS || swappiness > MAX_SWAPPINESS) + return false; + + for (seq = min_seq; seq <= max_seq; seq++) { + int gen = lru_gen_from_seq(seq); + unsigned long size = 0; + int zone; + + gen = lru_gen_from_seq(seq); + for (zone = 0; zone < MAX_NR_ZONES; zone++) + size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); + + if (seq + MIN_NR_GENS > max_seq) + young += size; + else + old += size; + } + return young > old * 4; +} + static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, struct scan_control *sc, int swappiness) { + int type = get_type_to_scan(lruvec, swappiness); DEFINE_MIN_SEQ(lruvec); /* have to run aging, since eviction is not possible anymore */ @@ -4977,7 +5005,11 @@ static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, return false; /* better to run aging even though eviction is still possible */ - return evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq; + if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq) + return true; + + /* Run aging if the preferred type is severely imbalanced across gens */ + return lru_gen_imbalanced(lruvec, type, max_seq, min_seq[type], swappiness); } static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, -- 2.39.3 (Apple Git-146)