From nobody Sat Sep 26 21:56:40 2026 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 444DF2E54B6 for ; Sat, 29 Aug 2026 07:42:19 +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=1787989340; cv=none; b=M3i7sYVmX/q0ezM3LyW0pJT+xciiKla9/7OxWXIFyNlH1D23+Gx+Eore5Ep2wjqaCC1m5Xrc7ySHu0OhbJW+HgqwprGQvrXXUBRjtfXLNbGo9aloghxo2GN4VkWCQkhBeso2qfvFUkGKqs2ZQX9FngI3vAib9qEut/cYL5fY37o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787989340; c=relaxed/simple; bh=bxI5llQDDHwdoVi7ZJ4fOKKs1z0W++CUOXMmbVQH9Ww=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=SNjAVZ+6RaZdCHiDSljJs95fsBMMfu83apjpL/WFP7DnNk2C8JlJ//w5n3RBrJaSz4blRjPbkq1ssMenIJ6mHmbK6/MOkkDqdZXNYHzkH8cP7Lm//VTbbzGkMaHj8XHHjcxScXBElCpUKJ0hbJDX727dFVjBP3GJwkNq6Pjq3Cw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ln6IGQ3W; 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="ln6IGQ3W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 851F71F00A3E; Sat, 29 Aug 2026 07:42:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787989339; bh=Ae9c4vZDXmNsxI4AdcLQro9NNVm5MPBZzf84/REbvA8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ln6IGQ3WV6IeHmrg10U5ceIy56PEPVtGtpAAax24IdWmKpTzpp+86hL3xcu3AaJqL INTubcliazpz9aoUI1sdyqJJ0+gULgCpcq07nzu5PWTc9rXbONFKfOPoeBVmuoi6nP jSoI+bKv0JTaeppyswbN02SjOZFC9N0FKhd7zXmHJchIjeWpLOgnlCxhkS2FFKJQfy i4x10maRQcYmjeY6+3JqjMvB2aKeIv0Q4FCgaGVoy0W/1cm4c9TZLl8wZLS5AxINJ3 r8ttq56E1GZfaWlBBezM0HVFmf2iZC83RSqOu1nKBfbbdONpI+bT7O4icpvyrgt0kh fzmmEZFuN3ZVQ== From: "Barry Song (Xiaomi)" To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: axelrasmussen@google.com, baolin.wang@linux.alibaba.com, baoquan.he@linux.dev, chenridong@xiaomi.com, david@kernel.org, hannes@cmpxchg.org, kasong@tencent.com, lianux.mm@gmail.com, linux-kernel@vger.kernel.org, ljs@kernel.org, lyugaofei@xiaomi.com, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, stevensd@chromium.org, wangzicheng@honor.com, weixugc@google.com, yuanchu@google.com, Barry Song Subject: [PATCH v2 1/2] mm/mglru: make type fallback logic explicit in isolate_folios() Date: Sat, 29 Aug 2026 15:42:03 +0800 Message-Id: <20260829074204.45304-2-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20260829074204.45304-1-baohua@kernel.org> References: <20260829074204.45304-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" From: Ridong Chen The for_each_evictable_type() loop in isolate_folios() is misleading: it does not actually iterate over each evictable type. Instead, get_type_to_scan() selects the type to scan, while the iterator `i` merely bounds the number of attempts. Make the fallback behavior explicit in the code and remove the opaque for_each_evictable_type(i, swappiness). Signed-off-by: Ridong Chen Co-developed-by: Barry Song (Xiaomi) Signed-off-by: Barry Song (Xiaomi) Reviewed-by: Baolin Wang Reviewed-by: Baoquan He Reviewed-by: Lian Wang --- mm/vmscan.c | 46 ++++++++++++++++++++++++++-------------------- 1 file changed, 26 insertions(+), 20 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index fdd13299a04a..35a233623368 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4838,35 +4838,41 @@ static int get_type_to_scan(struct lruvec *lruvec, = int swappiness) return positive_ctrl_err(&sp, &pv); } =20 +static inline bool is_single_type_reclaim(int swappiness) +{ + return swappiness =3D=3D MIN_SWAPPINESS || + swappiness =3D=3D SWAPPINESS_ANON_ONLY; +} + static int isolate_folios(unsigned long nr_to_scan, struct lruvec *lruvec, struct scan_control *sc, int swappiness, struct list_head *list, int *isolated, int *isolate_type, int *isolate_scanned) { - int i; - int total_scanned =3D 0; + bool type_fallback_allowed =3D !is_single_type_reclaim(swappiness); int type =3D get_type_to_scan(lruvec, swappiness); + int total_scanned =3D 0, scanned, tier; =20 - for_each_evictable_type(i, swappiness) { - int scanned; - int tier =3D get_tier_idx(lruvec, type); +retry: + tier =3D get_tier_idx(lruvec, type); + scanned =3D scan_folios(nr_to_scan, lruvec, sc, + type, tier, list, isolated); =20 - scanned =3D scan_folios(nr_to_scan, lruvec, sc, - type, tier, list, isolated); + total_scanned +=3D scanned; + if (*isolated) { + *isolate_type =3D type; + *isolate_scanned =3D scanned; + return total_scanned; + } =20 - total_scanned +=3D scanned; - if (*isolated) { - *isolate_type =3D type; - *isolate_scanned =3D scanned; - break; - } - /* - * If scanned > 0 and isolated =3D=3D 0, avoid falling back to the - * other type, as this type remains sufficient. Falling back - * too readily can disrupt the positive_ctrl_err() bias. - */ - if (!scanned) - type =3D !type; + /* + * We are running out of the current reclaim type. Fall back to + * the other type if allowed. + */ + if (!scanned && type_fallback_allowed) { + type =3D !type; + type_fallback_allowed =3D false; + goto retry; } =20 return total_scanned; --=20 2.34.1 From nobody Sat Sep 26 21:56:40 2026 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 0A1652E54B6 for ; Sat, 29 Aug 2026 07:42:23 +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=1787989344; cv=none; b=lky8feiIBARm+yEjWhLdO4+125/IV1DGyWoCu/BBPyhcpAx5WYrvelcgW3Fsl/xykAX5qMG3uXe+8yiUww+kZV2DR6TTlAETjHtIjmWXInzLeWWFjggTrnAc4YZitvgU7ZxsFLI7GMp6O1qtaB1WFqb+vtPi7jE1dbeaIPx8kIY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787989344; c=relaxed/simple; bh=nwFy8kCYzz8DtISgfMT58KJmiasHFztc+vuXUAB7SPA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=HGNVfTWJyo2ot6CwuDDZw5OBvktWdjKl1fBYtTfd14mJMj3gm+EkD7ChIkgyYvsjRfEI++GIsY7zrslNvrICWR3W/J8tD6x0ssXzdJd6WBVXWxDoAI8KszIHDKGq32F7x+tbWmHyZwX00d0elBZd2L6XpzAjOqT9vE6T3oINteY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UdOdwJ4L; 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="UdOdwJ4L" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66ACF1F000E9; Sat, 29 Aug 2026 07:42:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787989342; bh=E2pnQ2VYIoa3WiugIYl7Jp3rxV5b0Mqm4HU5w5Xg4uo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UdOdwJ4L1EiMt94CheIbvvTHNp40JARJbaPYbLKdR8O16tMBHur/IaGOamJRA1IQr Anbh5gB1YSRpAMeAGR8+BdMgXvvym5h8Lnc0DZCccOelPrSrVAjfkU4KCbhEEO1E62 LcLQ9GpnPEEJ0qAHuSwPowzHwy3hiIpHyaUM4JQAHUjcLWj9n2OPKES+hXvVwdgz8Q BN4XJyxv9v69l7FveED4v8uH6UAAYTEyDzCs751U8H8gWGYHo+U+3M/83eC98MQKTH ngSNvLH6KEqw7Ksl0hQ4DSnRAE1SDyWGY9sclcESg50ZZf7IJDzUJdGBQfOvT9ecHj t7ohmgZveEDQg== From: "Barry Song (Xiaomi)" To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: axelrasmussen@google.com, baolin.wang@linux.alibaba.com, baoquan.he@linux.dev, chenridong@xiaomi.com, david@kernel.org, hannes@cmpxchg.org, kasong@tencent.com, lianux.mm@gmail.com, linux-kernel@vger.kernel.org, ljs@kernel.org, lyugaofei@xiaomi.com, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, stevensd@chromium.org, wangzicheng@honor.com, weixugc@google.com, yuanchu@google.com, "Barry Song (Xiaomi)" Subject: [PATCH v2 2/2] mm/mglru: make retry logic explicit in isolate_folios() Date: Sat, 29 Aug 2026 15:42:04 +0800 Message-Id: <20260829074204.45304-3-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20260829074204.45304-1-baohua@kernel.org> References: <20260829074204.45304-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" The existing mainline code retries the same type once in a rather subtle way. `for_each_evictable_type()` may provide one more iteration, allowing the same type to be retried if we scanned some folios but failed to isolate any due to protections, promotions, or races. This patch makes the retry behavior explicit. Signed-off-by: Barry Song (Xiaomi) Reported-by: Baoquan He Reviewed-by: Baolin Wang --- mm/vmscan.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 35a233623368..718f59ffc688 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4852,6 +4852,7 @@ static int isolate_folios(unsigned long nr_to_scan, s= truct lruvec *lruvec, bool type_fallback_allowed =3D !is_single_type_reclaim(swappiness); int type =3D get_type_to_scan(lruvec, swappiness); int total_scanned =3D 0, scanned, tier; + bool tried =3D false; =20 retry: tier =3D get_tier_idx(lruvec, type); @@ -4871,9 +4872,18 @@ static int isolate_folios(unsigned long nr_to_scan, = struct lruvec *lruvec, */ if (!scanned && type_fallback_allowed) { type =3D !type; + tried =3D true; type_fallback_allowed =3D false; goto retry; } + /* + * We scanned some folios but failed to isolate any due to promotions, + * protections, or races. Retry once to avoid a larger loop. + */ + if (scanned && !tried) { + tried =3D true; + goto retry; + } =20 return total_scanned; } --=20 2.34.1