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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E0A1640003 X-Stat-Signature: tqq4sdt6qpqd8dye6xf7796aag8uzqgf X-HE-Tag: 1787989339-326671 X-HE-Meta: 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 3DW/zJKK 4mmrgVA/42uH+6auO63cMi6s0IG7nlOSL9feYUUtYy6f9hATfeaeemJ3OCoB2bb31SIdujAExfP3ccS3Tsf9kB0AoscIOqWM8+Dv2FBwT4TyvwSi72GeNWveuyqVX50vKx173D92JEuUGqJ6+oklT1CD33xUoWctFI32Cx3PcRuWcMQX09tojC5XkGS4E0NE5bb183bm7avX6/EWC/2PQhHD2lmTrWPBz0TsGIDGTuaifKKk3d6AthrpxvvmC/W/IQOIXS3loJ5Wyk1G3s/wppRsinFWrFve/WYKgaU4yvNpV6l7etpHfzTRPoyBTuZWtIGFR4BjJ51ZEj9telV5Q3/L1s8TuTsZhJrgRea2x54Qqw0uhdFHNu2RoSmUHQRyFeIEx Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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