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Shenoy" , Swapnil Sapkal , Shrikanth Hegde , Chen Yu Subject: [RESEND RFC PATCH v2 15/29] sched/topology: Introduce percpu sd_nohz for nohz state tracking Date: Mon, 8 Dec 2025 09:27:01 +0000 Message-ID: <20251208092744.32737-15-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251208083602.31898-1-kprateek.nayak@amd.com> References: <20251208083602.31898-1-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: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS3PEPF0000C37F:EE_|CH1PPFA0A5C3BCA:EE_ X-MS-Office365-Filtering-Correlation-Id: 7d6afd6a-31db-488f-737d-08de363ca871 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|82310400026|7416014|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?iu02FTuHEXWWlBAkcuA9dCM80kTjEioEMM22ltWtu0EbsUQZO9TZN53j6UX4?= =?us-ascii?Q?9Wkfq/HKLjRZJHkQOJ6ONmwU11/uDnitAm74vkfiaBus8kpCPncCIXD4wZ/f?= =?us-ascii?Q?alZWcIczzKiEkbEnOF+QxE/7MfcXiQNt6k+lUanCKmFIbqSaodrdQxw2SboB?= =?us-ascii?Q?i4p2nSWLUCL92Tt74Echz7yONuoPItt+wRdL1/dwfNI5I1qWI04Ytek4V7ne?= =?us-ascii?Q?kY8gUwjj/C4WbhbImJxj86jl+6KprGozgCCKR2CnS4SJn2TiqMKj45D0vneY?= =?us-ascii?Q?iW0HXwFqyspRpkP+LvmUc/vZTWycyyDqcqtNU+/cx5YHEzPedvqKUf+SfCnF?= =?us-ascii?Q?reuni65uJLiA9DTK9hhMVexIb4A7UFLZ1kxCn2PGbpweURlcW4ro41SwRch6?= =?us-ascii?Q?lMwvkyEzUrb/TPq3P+7y21h66IfASd5lGX3H8vewTR71evfIGLh13bll2WtT?= =?us-ascii?Q?LfLAqnAa6BAdR1A/p15rPYq4oL+KeZ9AHcm0rUIup6gEEIX461CbGQJjijnX?= =?us-ascii?Q?oodh240bTSkS03U8fZcuu9EewQhBzw/oALbzD2f0hu7mG/OLdRAHDw6NutlI?= =?us-ascii?Q?Kvt2TGGG2/mWk43rWOSPrjkwAwyc2QEEDpOowLHMD8i2awPzGyBEnkTTey82?= =?us-ascii?Q?/7zpjHINqiMbIcEtiiVZVF667RYVihlarkGyz8wCpMjSUkgeOh1ICt9BBOKP?= =?us-ascii?Q?G9IJLQ2t2pNXcBOtJCpejQxKV2e3Z0tW9yEyXEJ3xh1QhFQMMCjivrrWBvN4?= =?us-ascii?Q?6PTJY7+x9hscJbm3f2U6UcKXI1ney85Rhr5nh4+n+pRYdubRb6fef+O6xJ8e?= =?us-ascii?Q?f58LEZ9tBmOr2iAcTevUoSHcCOqSbODG5lDYiL5jAEvgIHi+pdF6HcC8GxsS?= =?us-ascii?Q?BIFoDo/WzN4IvubEMb6zK47JU/N90gmWiCdwIzeOfvm2jqVjxtA3WT0y1xfF?= =?us-ascii?Q?OpgbnkYz64NiRtouMgFlhiR6bqtRKj1ccPFXHR6VCZmz9hYI0tg7Rn8Yhngq?= =?us-ascii?Q?zxO+cjQ9iK6v/7huFzYMGY6ZJ6wrtVXmQV2c9uklXHB/zFsKxqg4fjz2jR3w?= =?us-ascii?Q?f7IIn1H8ZTlyvTBg0XmfwUbi2bH66elV3qjubjvmXdScsj52/PwKIALa0e+u?= =?us-ascii?Q?NY/+nW+bzDpX4IzRCWCJAHTz22dfZIU4pcuXC8KhnAro0vnHbI05FaYVL+62?= =?us-ascii?Q?Wa/XmRRWzuE3o9PrRd2i5LvwMSO3OX1saxEvfTk+P4SgDuwBDbV2HRJfbPYO?= =?us-ascii?Q?ViS7FPThOMXsXrBBfcUpgLuGNWYWScP51LwTeLvOgGbZWxxRINmC1czg1R1l?= =?us-ascii?Q?aopT1U2JRGF0q36ZkkQa0Kvi89t9rgKalMjg2wQGmr+E8sEmdS+ieAWdBAEU?= =?us-ascii?Q?6Pxt7F/KuzTZXIYWhBWJDQ9DOXQJF5emQXoq12gvc16aCkb1/E9xPTPDV8G6?= =?us-ascii?Q?zY9oylyhkXrgU4muQ/4Vnm6ddX0h685TAbko78UY8egdiRY8MSH3M2VThhVH?= =?us-ascii?Q?fP8mcHUDYmI0F9wWS7NqEEETKJGIWiR+uxaUWmDpnFzazJ2ynawZWeOhxz26?= =?us-ascii?Q?6hgI+pgPtjb1Y0JX26g=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(36860700013)(1800799024)(82310400026)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Dec 2025 09:32:08.4353 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7d6afd6a-31db-488f-737d-08de363ca871 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF0000C37F.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH1PPFA0A5C3BCA 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 fef3826a258f..be7e818687c7 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12555,7 +12555,7 @@ 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 @@ -12585,7 +12585,7 @@ 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 7b0f9fbfc65b..be52ebaf0143 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -3263,6 +3263,8 @@ 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 3a0740be9fcd..5c399ca1f4a1 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 2.43.0