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Howlett" , Vlastimil Babka , Yu Zhao , Zi Yan , Qi Zheng , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Kairui Song References: <20260818-mglru-flags-cleanup-v1-0-8dbbdac0d28c@tencent.com> <20260818-mglru-flags-cleanup-v1-5-8dbbdac0d28c@tencent.com> From: Ridong Chen In-Reply-To: <20260818-mglru-flags-cleanup-v1-5-8dbbdac0d28c@tencent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: sod7pew59hu1m7sh5qwr91jp3p79xzfm X-Rspamd-Queue-Id: BB79E180006 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1787193247-954613 X-HE-Meta: U2FsdGVkX1+JxfQ0tdMw0mW3TpZXbYIUHZ3PHv2ykZFVMEMz0ouN3c3Ueco0DQYkycLIxAAAPab4f8DNmTGWRXguFPmZaM6/pnt24OfwEnlQZTsbOcuTxi4CkTpHMB1xo/CGbdjFWfzOg9mNZJg62+tfsk9+2Mk5v0xsKZZAomRgza6Kv1+wmi22iZFK2xD+sEErPVVmsyMB2+O9XhPQwK2EphjNQyWkFea2sfMpFJvxL3C/w4tE4p+mNFbevBWgbRCBD0dh8u+wd3/udSkorDuDVYSbdcBAFqFEm3WXos5jdu2tcSCwTrXuX6+2Z4MLSDyU3s25P1hq5csSVNdxUHXj/KbstIZQIwOrEBO5iUNUekH4LzUxCZeShMr55OZuxEc8ombiKzVQ6+FPWzxRtQperSuPBL1i/Evkk+uXj3i7HK8aXt983yxgCIA9F59CbSRDDMdYdAlzQ+TzS0l7dEXTZETnJ4Kq1eDOO57BcAErR6yNMKOEir1Qa6ubk3yRJAbrmLZ5XIcSqUr1xgx1Od65SHSB3VjQTH1lEIaIigRG/kUX3/cNlfGrMuH3pRATte5A9aNEWcKJD8pUIUedgRJuiySHGLkVhWal87s93Y5EwShVd4x6RgDH4NVx3ldsj6P2PXkcPeRWOeya3/p7TZ2aYctMlx0/PseA7AEy+HjcNFkWFSrt30eSrnvFkKkFKi/oy4tlMMJbrtKpDGlJAt+7oyXOmOuqtcu5SlxoY6roxyk4iX3+l9C2Oca3iwJqXJEcicSZtwaiUD/Ai1FTlb8hi0cEHcb9CP1EMORkPxvoRGU2Mnq53s3jrknbUt7GuW5Gm5G8It9vxGfihBskrp192t7516XZpJGRZbPpouxJjSRGwZUtljVHpfO3dGhf4OKUf6BG90geVrP6L3Z8mJNmh7gtqqsTUd3ywD+zxL7+tyoHDWoexpQUs+dx5z4uYx1TsyNw1WpzooGf3Td 1zmAhYet ZcykrZBRwXdD2akAXCkXhHLiwrBcz2O8a43qeadANfcoR9qMMrt9N3Fml18RoKgQDFfeOFZ30Wtu3GS3iLZeF+avR24+ct4cXwKQbyRIMfQH7ArCQEgea996ld+3HiLp6N8TQDTNilzFns7NZD4VaqeDixWMKbPP4NHr5jBj9X5V0WiNEKyLIOC4b49+pvRhf5dV3ACyk8lcE1O4geBIElEHBZ1Yjj5a9FOblg5lrEe4V4Zy9r2imnn5D1bnNZrmC5G/6qIdlzB75oDpAwzj78LhmoB+vhi4a/FH9G8hYQFmca3km1uGvFUbtGPcs1bWaB4UmzqBSbw/LOb875o17KQLoPL5412DJd3aohROeN5vAFdWiHMfK9y2tdaLvgZOA85/E Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/18/2026 1:38 PM, Kairui Song via B4 Relay wrote: > From: Kairui Song > > read_ctrl_pos() encodes the tier range in a single "tier" parameter > via "tier % MAX_NR_TIERS" as the start and "min(tier, MAX_NR_TIERS-1)" > as the end. This is hard to follow, maintain, or extend. Tier values > 0..3 select a single tier, while tier == MAX_NR_TIERS selects the > full range. > > Replace it with explicit (tier_min, tier_max) parameters using a > closed [tier_min, tier_max] interval, and add LRU_TIER_MIN and > LRU_TIER_MAX for the tier bounds. The call sites now become > self-documenting: > > - get_tier_idx: (LRU_TIER_MIN, LRU_TIER_MIN) for the first tier, > (tier, tier) for each subsequent tier > - get_type_to_scan: (LRU_TIER_MIN, LRU_TIER_MAX) for the full range > > No functional change. > Just like LRU_GEN_MAX and MAX_NR_GENS issue. Why do we have to add LRU_TIER_MAX, can we just use [tier_min, MAX_NR_TIERS)? > Signed-off-by: Kairui Song > --- > include/linux/mmzone.h | 2 ++ > mm/vmscan.c | 18 ++++++++++-------- > 2 files changed, 12 insertions(+), 8 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 32d9354a754f..d0b5c6217d25 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -492,6 +492,8 @@ enum lruvec_flags { > * folio->flags, masked by LRU_REFS_MASK. > */ > #define MAX_NR_TIERS 4U > +#define LRU_TIER_MIN 0U > +#define LRU_TIER_MAX (MAX_NR_TIERS - 1) > > #ifndef __GENERATING_BOUNDS_H > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index a819be6b7ae9..a613bb8d7271 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3198,8 +3198,8 @@ struct ctrl_pos { > int gain; > }; > > -static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, > - struct ctrl_pos *pos) > +static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier_min, > + int tier_max, int gain, struct ctrl_pos *pos) > { > int i; > struct lru_gen_folio *lrugen = &lruvec->lrugen; > @@ -3208,7 +3208,7 @@ static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, > pos->gain = gain; > pos->refaulted = pos->total = 0; > > - for (i = tier % MAX_NR_TIERS; i <= min(tier, MAX_NR_TIERS - 1); i++) { > + for (i = tier_min; i <= tier_max; i++) { > pos->refaulted += lrugen->avg_refaulted[type][i] + > atomic_long_read(&lrugen->refaulted[hist][type][i]); > pos->total += lrugen->avg_total[type][i] + > @@ -4804,9 +4804,9 @@ static int get_tier_idx(struct lruvec *lruvec, int type) > * This value is chosen because any other tier would have at least twice > * as many refaults as the first tier. > */ > - read_ctrl_pos(lruvec, type, 0, 2, &sp); > - for (tier = 1; tier < MAX_NR_TIERS; tier++) { > - read_ctrl_pos(lruvec, type, tier, 3, &pv); > + read_ctrl_pos(lruvec, type, LRU_TIER_MIN, LRU_TIER_MIN, 2, &sp); > + for (tier = LRU_TIER_MIN + 1; tier <= LRU_TIER_MAX; tier++) { > + read_ctrl_pos(lruvec, type, tier, tier, 3, &pv); > if (!positive_ctrl_err(&sp, &pv)) > break; > } > @@ -4827,8 +4827,10 @@ static int get_type_to_scan(struct lruvec *lruvec, int swappiness) > * Compare the sum of all tiers of anon with that of file to determine > * which type to scan. > */ > - read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp); > - read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv); > + read_ctrl_pos(lruvec, LRU_GEN_ANON, LRU_TIER_MIN, LRU_TIER_MAX, > + swappiness, &sp); > + read_ctrl_pos(lruvec, LRU_GEN_FILE, LRU_TIER_MIN, LRU_TIER_MAX, > + MAX_SWAPPINESS - swappiness, &pv); > > return positive_ctrl_err(&sp, &pv); > } > -- Best regards Ridong