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Shenoy" , Swapnil Sapkal Subject: [RFC PATCH 09/19] sched/topology: Introduce percpu sd_nohz for nohz state tracking Date: Thu, 4 Sep 2025 04:15:05 +0000 Message-ID: <20250904041516.3046-10-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250904041516.3046-1-kprateek.nayak@amd.com> References: <20250904041516.3046-1-kprateek.nayak@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To satlexmb09.amd.com (10.181.42.218) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA2PEPF00001506:EE_|DS0PR12MB7927:EE_ X-MS-Office365-Filtering-Correlation-Id: 7686ed8d-2667-4cbf-6804-08ddeb6a1117 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|82310400026|36860700013|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?nyuhlNXy+NXArKsGa3HF07VAS9ajcp7aj7jgaw6udApppjZJT2J0rypBIhGQ?= =?us-ascii?Q?GjoWVAVZbTtMAygJPfvjKxXGs6/vn8SXUxPN64d9BMVT5u7WKS3gr3WJTbnl?= =?us-ascii?Q?gUGGmPp9r1KCHL+zegMMHAaXm6UZrGuPbn/Pmr5JHqYTIJn34ve+EkfSBA77?= =?us-ascii?Q?CDbYZEim7TssFpoftgloUpC9+wMWt4Ml5y3khU2U6dFg0U8YID3ctlkrMsr/?= =?us-ascii?Q?QX7xgwv94+Knyovx4Hy9RmJ6epnRGMmY8qIYSxapNPhhNT8WRHBI8wxOLFDF?= =?us-ascii?Q?D8SlaO5zXPIwOEuuNl8aEFXqvxELq2u8WJxeh4ohhQVwW/YMU3m+DLPsbYdI?= =?us-ascii?Q?TkwIg7rMOS9joaTANym4jnZjCuXltFi7F0rlPNMkj+BhxPnhyNufGfgl2O3Q?= =?us-ascii?Q?+jcPQ6HGGRKpeJQ1SjZua47xEvwOKG+iYF7qrhvu2NO7UMvssvCePo4Ykc1i?= =?us-ascii?Q?heoP8XIv1csgqFKVyYc5Ewuikn6VSE+ilkk40AJD6N4Y5Xn/FmnQQYxM+v9f?= =?us-ascii?Q?8pQ18vNOgv8Fte4pllQELXP+eEXARsJKeqNL8YF95oXqjxYSQ4aojVQSM/Ty?= =?us-ascii?Q?IF5hZzT0Rv6yFY1hBfa2QR6xUaw+EEViTGhSFOoAo2o3/AJsvolnFiXnuutg?= =?us-ascii?Q?tqTvRZqUUPRcFjuWczIAMSxOaCcSr07WZaF/D23GH1d3CcmurXcmCUmCSalx?= =?us-ascii?Q?PQ27bKt3Pwo6f1R/j9fw4cQrO0GD4ZQxtrz0lVHx4qFybNMG5By8EVCa3buP?= =?us-ascii?Q?8tXtaH5NWluy2fPzvgWWduU84okoYEi4Y1pZqUiLn1nzKOOz4wZjgDY7XYCu?= =?us-ascii?Q?ASo9pwRCZisa2kzEqLFq9sx0YkO8EZymiDLSFT9KfzDNc20IVR4Sk1hX8/lT?= =?us-ascii?Q?5def8wylbtVjeC1VZtI3IawUUGxPDp5mg+FdeAo9xF4auBtVkszgoleEW3PX?= =?us-ascii?Q?Bn5PFY5RT0/GjYXwtGXayMyul9dYmWcTeFokgbZJ2YpgtD3PFxB8fwjD+NZW?= =?us-ascii?Q?odWo6Q/Ha6p3zK95cI3BZpmeOpTyB8jkpVSratoO+RkYgHam1T0tn7eVvWq6?= =?us-ascii?Q?Q+4MXsLMWjxrq8gfdyZ7EMmaGM2k7E+GPVIMfZKrNi7TKaKYZgYFeT0FeFx2?= =?us-ascii?Q?xdEp4u3qcgVgT+h1356shB490GxhToLks9zpoWPxDw/HtwCVOEMyeeSylGvz?= =?us-ascii?Q?x1dK6tERF4Thqqyf/lZ/KY/olkEqEcCDCX+qhEFbvnXLyN9GbHmX5sHtM6lK?= =?us-ascii?Q?5SDaWVsuLuQe0s9CWVwf2ASgvZKFecfUu4/JAi46UevkzPQVDg2Me5i/hVU/?= =?us-ascii?Q?KhkXXIkxFJqYIakX4pOOIE2DbyrH7ZRPHKqqTSnZ7fSYtqlX1/+lgzfHEaQz?= =?us-ascii?Q?iupGAwsirjoNEh5m3F98tjduTRIuUOZU3RDZ7Wj9wHL3eFrHagQz7W/idw7g?= =?us-ascii?Q?ju3p1dEJ38TIxvNZyVclJYiik+YEWmTf7zLKUoUyhG+WgQR0XvYZno1+kFJQ?= =?us-ascii?Q?3xPTZRytDvc4q7O2ZqMZ82q7WCp2jblN+NFr?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(376014)(7416014)(82310400026)(36860700013)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Sep 2025 04:18:14.1547 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7686ed8d-2667-4cbf-6804-08ddeb6a1117 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SA2PEPF00001506.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB7927 Content-Type: text/plain; charset="utf-8" Add a per-CPU "sd_nohz" variable to track domains in the local CPU's hierarchy that have "sd->shared" set for nohz idle tracking. Convert cpu_set_sd_state_*() to use "sd_nohz" instead of "sd_llc" increasing the scope of tracking to all CPUs with non-NULL sd hierarchy attached as opposed to just those CPUs with a "sd_llc" domain. "sd_nohz" will be used in a subsequent commit to transition nohz_balancer_kick() to use the distributed nohz idle tracking. Reviewed-by: Gautham R. Shenoy Signed-off-by: K Prateek Nayak --- kernel/sched/fair.c | 4 ++-- kernel/sched/sched.h | 2 ++ kernel/sched/topology.c | 22 ++++++++++++++++++++++ 3 files changed, 26 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index dee0ded7f40d..624b3753c818 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12451,7 +12451,7 @@ static void set_cpu_sd_state_busy(int cpu) =20 guard(rcu)(); =20 - sd =3D rcu_dereference(per_cpu(sd_llc, cpu)); + sd =3D rcu_dereference(per_cpu(sd_nohz, cpu)); if (!sd || !sd->nohz_idle) return; =20 @@ -12481,7 +12481,7 @@ static void set_cpu_sd_state_idle(int cpu) =20 guard(rcu)(); =20 - sd =3D rcu_dereference(per_cpu(sd_llc, cpu)); + sd =3D rcu_dereference(per_cpu(sd_nohz, cpu)); if (!sd || sd->nohz_idle) return; =20 diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 9ae3e2993641..35ffb3926334 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -3097,6 +3097,8 @@ extern void cfs_bandwidth_usage_dec(void); =20 #define nohz_flags(cpu) (&cpu_rq(cpu)->nohz_flags) =20 +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_nohz); + extern void nohz_balance_exit_idle(struct rq *rq); #else /* !CONFIG_NO_HZ_COMMON: */ static inline void nohz_balance_exit_idle(struct rq *rq) { } diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d71c60d99313..f230892528c7 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -466,6 +466,8 @@ struct s_data { =20 #ifdef CONFIG_NO_HZ_COMMON =20 +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_nohz); + static int __fallback_sds_alloc(struct s_data *d, unsigned long *visited_n= odes) { int j; @@ -532,6 +534,23 @@ static void claim_fallback_sds(struct s_data *d) } } =20 +static void update_nohz_domain(int cpu) +{ + struct sched_domain *sd =3D highest_flag_domain(cpu, SD_SHARE_LLC); + + /* + * If sd_llc doesn't exist, use the lowest sd for nohz idle + * tracking. cpu_attach_domain() already ensures sd->shared is + * assigned for the lowest domain if sd_llc doesn't exist after + * degeneration of the hierarchy. + */ + if (!sd) + sd =3D rcu_dereference(cpu_rq(cpu)->sd); + + WARN_ON_ONCE(sd && !sd->shared); + rcu_assign_pointer(per_cpu(sd_nohz, cpu), sd); +} + #else /* !CONFIG_NO_HZ_COMMON */ =20 static inline int __fallback_sds_alloc(struct s_data *d, unsigned long *vi= sited_nodes) @@ -542,6 +561,7 @@ static inline int __fallback_sds_alloc(struct s_data *d= , unsigned long *visited_ static inline void __fallback_sds_free(struct s_data *d) { } static inline void assign_fallback_sds(struct s_data *d, struct sched_doma= in *sd, int cpu) { } static inline void claim_fallback_sds(struct s_data *d) { } +static inline void update_nohz_domain(int cpu) { } =20 #endif /* CONFIG_NO_HZ_COMMON */ =20 @@ -804,6 +824,8 @@ static void update_top_cache_domain(int cpu) =20 sd =3D lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY_FULL); rcu_assign_pointer(per_cpu(sd_asym_cpucapacity, cpu), sd); + + update_nohz_domain(cpu); } =20 /* --=20 2.34.1