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 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: 8bit 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) --- 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); } +static inline bool is_single_type_reclaim(int swappiness) +{ + return swappiness == MIN_SWAPPINESS || + swappiness == 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 = 0; + bool type_fallback_allowed = !is_single_type_reclaim(swappiness); int type = get_type_to_scan(lruvec, swappiness); + int total_scanned = 0, scanned, tier; - for_each_evictable_type(i, swappiness) { - int scanned; - int tier = get_tier_idx(lruvec, type); +retry: + tier = get_tier_idx(lruvec, type); + scanned = scan_folios(nr_to_scan, lruvec, sc, + type, tier, list, isolated); - scanned = scan_folios(nr_to_scan, lruvec, sc, - type, tier, list, isolated); + total_scanned += scanned; + if (*isolated) { + *isolate_type = type; + *isolate_scanned = scanned; + return total_scanned; + } - total_scanned += scanned; - if (*isolated) { - *isolate_type = type; - *isolate_scanned = scanned; - break; - } - /* - * If scanned > 0 and isolated == 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 = !type; + /* + * We are running out of the current reclaim type. Fall back to + * the other type if allowed. + */ + if (!scanned && type_fallback_allowed) { + type = !type; + type_fallback_allowed = false; + goto retry; } return total_scanned; -- 2.34.1