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bh=/0gHFotsVKjTxWximSJ39pG4OGpTc8wpx2/QFZtytuQ=; b=jDcI0pwta5PzNVv3altbatnoW8kW4S1BsLaT3p+MPlEgpbALK1c1lUYGK6KtG9zzqFF5tORfMAPSkuuY41PAsVT3iqFGCE00DbefisYCWOjBH9+xPx4zZ6MwOXrr1e7zW//knAznhsHolTijsBrS7io6mPciYX16j8p4n3NjvYY= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=os.amperecomputing.com; Received: from PH0PR01MB7975.prod.exchangelabs.com (2603:10b6:510:26d::15) by BN5PR01MB9177.prod.exchangelabs.com (2603:10b6:408:2aa::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8835.29; Thu, 19 Jun 2025 03:20:20 +0000 Received: from PH0PR01MB7975.prod.exchangelabs.com ([fe80::6926:a627:118e:8050]) by PH0PR01MB7975.prod.exchangelabs.com ([fe80::6926:a627:118e:8050%6]) with mapi id 15.20.8813.020; Thu, 19 Jun 2025 03:20:20 +0000 From: Huang Shijie To: mingo@redhat.com, peterz@infradead.org Cc: patches@amperecomputing.com, cl@linux.com, yang@os.amperecomputing.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, Huang Shijie Subject: [PATCH] sched/fair: set the se->vlag strictly following the paper Date: Thu, 19 Jun 2025 11:19:42 +0800 Message-Id: <20250619031942.25474-1-shijie@os.amperecomputing.com> X-Mailer: git-send-email 2.40.1 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SY6PR01CA0064.ausprd01.prod.outlook.com (2603:10c6:10:ea::15) To PH0PR01MB7975.prod.exchangelabs.com (2603:10b6:510:26d::15) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR01MB7975:EE_|BN5PR01MB9177:EE_ X-MS-Office365-Filtering-Correlation-Id: 9cf2dd41-a4a0-4c0e-3fb6-08ddaee03865 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|52116014|1800799024|366016|38350700014; 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charset="utf-8" From the paper, the lag should follow the limit: -r_max < lag < max(r_max, q) But current code makes the lag follow the limit: -max(r_max, q) < lag < max(r_max, q) This patch introduces limit_hi/limit_lo/r_max, and make the lag follow the paper strictly. Signed-off-by: Huang Shijie --- kernel/sched/fair.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 83157de5b808..102d263df330 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -694,14 +694,17 @@ u64 avg_vruntime(struct cfs_rq *cfs_rq) */ static void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *= se) { - s64 vlag, limit; + s64 vlag, limit_hi, limit_lo, r_max; =20 WARN_ON_ONCE(!se->on_rq); =20 vlag =3D avg_vruntime(cfs_rq) - se->vruntime; - limit =3D calc_delta_fair(max_t(u64, 2*se->slice, TICK_NSEC), se); + r_max =3D 2 * se->slice; =20 - se->vlag =3D clamp(vlag, -limit, limit); + limit_hi =3D calc_delta_fair(max_t(u64, r_max, TICK_NSEC), se); + limit_lo =3D calc_delta_fair(r_max, se); + + se->vlag =3D clamp(vlag, -limit_lo, limit_hi); } =20 /* --=20 2.40.1