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Wed, 02 Sep 2026 06:53:35 +0000 X-Mizu-Trace-ID: 6addee44da3240d2 X-Migadu-Flow: FLOW_OUT Date: Wed, 2 Sep 2026 14:53:28 +0800 From: Baoquan He To: "Barry Song (Xiaomi)" Cc: akpm@linux-foundation.org, linux-mm@kvack.org, axelrasmussen@google.com, baolin.wang@linux.alibaba.com, 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 Subject: Re: [PATCH v2 1/2] mm/mglru: make type fallback logic explicit in isolate_folios() Message-ID: References: <20260829074204.45304-1-baohua@kernel.org> <20260829074204.45304-2-baohua@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260829074204.45304-2-baohua@kernel.org> X-Stat-Signature: kumo6yqebdim49t7gfrw6bwehofow9cg X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: AC1FB40003 X-Rspam-User: X-HE-Tag: 1788332017-80663 X-HE-Meta: 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 nA1pg9N7 3N+0nEnZOI09cgXnIUfSocztPAoyWFyxjp/jhsy1HHKHLFCqirJCTynkw08GFnKPptILrEI+njsecSyPBRRIY69cP0KkOdpINCzftnacUboqpHVOclwZJ+Y4bZF/nF1soYt/3BQM8Tdqp0kKL3Iszdte3LC/37by6eO7Hf9tv1kydglWcEu0CY2UqUMyA8u48YK2VWzsmH6yDoMjfoB8/HjqpEw1Yh0XXyHmqPqNBh+5EuZoSV1nzRH0qrxwdi75yXJ9F3DjQiZi4kUdFavMP0pfWNha+5WAUugKzhKRQw91HHfZPTG7RwSs8j5FzmNHseMPXyXM+SjwrXXYAMP9SXlfQnqe9EQHzCKgi6+bYKMFlrPSd0lcu+eWzaJ9eMg7w4LNwiYmXOTuN9PnDKcYeP88x7U2hB1eAan00pNfUAd0/tbDaoEwH7RscQpTI27Z0kbCu Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 08/29/26 at 03:42pm, Barry Song (Xiaomi) wrote: > 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(-) Reviewed-by: Baoquan He > > 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 >