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Shenoy" , Swapnil Sapkal Subject: [RFC PATCH 19/19] sched/topology: Add basic debug information for "nohz_shared_list" Date: Thu, 4 Sep 2025 04:15:15 +0000 Message-ID: <20250904041516.3046-20-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: SA2PEPF000015C6:EE_|MW6PR12MB8952:EE_ X-MS-Office365-Filtering-Correlation-Id: 4219fe04-eb74-40ac-0e69-08ddeb6a80d9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|376014|7416014|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?deQX2YvzHrGm/jswrAGEl9pTAkTBEQow87XnL/4W9/2pL85ld620GsQHyC4g?= =?us-ascii?Q?t4BRvRjtY9LrNjnHk6cCQWOvzPRzYZrW3QWGHt8pkC4xqBisMMJ3cdQ4szyt?= =?us-ascii?Q?iozTF5QZoSAyTnBlo+zYDaNrF2OOGkcz/9X9xtZzfpWKcH6royHd2aL/FekZ?= =?us-ascii?Q?Ow8wzlhedSyXZW2X+vxoRPeektDzfF6pWsnZe6rB4f3SpUIl9Bn0cFLcyg84?= =?us-ascii?Q?petaNu6iI0DzuzDyYgT+u3GTXAeW22rpmXUc9bKMkDtKC+uxZIknX9TX+cU9?= =?us-ascii?Q?XMHOV/BDiS0L+NX7csEI7PhmWAmsZGPiW4W140YP+/h5zkMoxlgaJlozwvMU?= =?us-ascii?Q?Bjxh/j76UOai6fjclXLgo1VoZmd64cFRPRQJBvJjCXJ22gtaSfp+ZQhR2G4R?= =?us-ascii?Q?DcIN3JWJL0bYyFQn5P8e3etsmVeRuE0l/FvOg+yHr/e29Hc5AdIqTftuBvmk?= =?us-ascii?Q?3LwMSdzCgvdJwHMCeRFK9YOPlh6x41vmzCNtWJad01iS5vHckftZrDKiyVBt?= =?us-ascii?Q?Fe4hCOJLwSqriw6gD/nSosO/wJzl91CrYWIBuOK1KqigHIfHaq33X+8X3Put?= =?us-ascii?Q?Vlf08ZVrDK95ZTSi2N9V4B60E1biU9xRwMKMDVtXPW2tkz3QLoQPvqg71O+D?= =?us-ascii?Q?pGQ622hQ299nNqadjHT2fF07RgP90D41Gk1y8Livu8xOIoMbNkDIuZSuN1hl?= =?us-ascii?Q?7Epjo6Yewun/hhPeHL4Y/wqYuaHvHm7/dVMlg8JmSZs7nzD3bUnprtxXn7/q?= =?us-ascii?Q?i+QUWdzkEq5s/+dHbnXw62cWHP2zmYuJGOAmpZEIKVWlN29DvTG5lIYNPJb7?= =?us-ascii?Q?g+9O4Ekt5Z5CchotFbv5QozBzulSZ+jk7Puafhqq95UfpVyYt497bi30LmP1?= =?us-ascii?Q?ElECoZUeoasNgsZpD/SHkS8Rht4lc7Yu5LyK/y5Uze06KhibsWIoAMsQ0L+V?= =?us-ascii?Q?6g49X/ygEB8d80bVbJiKdI552m0CDXGE4PL6+Ww8wRFi0tOCyc6TqSSSe5Hn?= =?us-ascii?Q?LOv2/zTMfw/2YqvfYhQFUxukqU5RI7Yo2ln4ZNdTS+Oh/ra67qe3IMIDVVqs?= =?us-ascii?Q?MXZIKjQ1RR34goqfl58XWoamqDbByXMBvRXiXFdQMNyPnLnY+fuC8m4+f43v?= =?us-ascii?Q?eGc+2NcN/oLrLa1/SdTu0fPPe6XU+fQwwVZK2BT0CpHRX6JDkCbnR8q+9kUX?= =?us-ascii?Q?Es21Z/qJYp3XZOeVAsU46ObWDQTt1/eV0tNnGl5JQVzVfGsp6qLyl/kY/ld2?= =?us-ascii?Q?q6uh8NNsueNZZEQx7t+Ci1XzILbFlObrdfIe511TFFOzR7kw28MoXNdKigql?= =?us-ascii?Q?pdEg7B01n6o8Q4j5m04ZRXp0Wa5XtwUGRefXo4jj/EkgCphHPhTH5NnCmYnJ?= =?us-ascii?Q?O1uemCmhpBCLTX2vqJO8hqYo+Jqx4uVqieOrZBA5r2ZjBB3TVkkXpe+WTlsr?= =?us-ascii?Q?QB4cUIiCuyWtVR336TRLXgvtr6TQNOgTDq0wSsYJhzAnpaB6KAyn3ih2C/Nv?= =?us-ascii?Q?2Lx9W1eis78TQcZa1jZICd3PhJ6fJ7Vkwpn4?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB03.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(1800799024)(376014)(7416014)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Sep 2025 04:21:21.6499 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4219fe04-eb74-40ac-0e69-08ddeb6a80d9 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=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SA2PEPF000015C6.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW6PR12MB8952 Content-Type: text/plain; charset="utf-8" Introduce debug_nohz_shared_list_update() to count the number of entries in "nohz_shared_list" after each list modification. XXX: There isn't a great way to jump from a sched_domain_shared object to the sched_domain struct that references it which prevents printing more information about the sched domain that was linked with the shared object. Signed-off-by: K Prateek Nayak --- Note: Something in this patch upsets the LOCKDEP + sched_verbose cmdline combo and hangs my system soon into boot. LOCKDEP alone or sched_verbose cmdline alone doesn't have this effect and until Patch 18 even the offending combo runs fine. DEBUG_LIST didn't point to anything and I'm still scrathing my head on why this may be the case (maybe I need some glasses). --- kernel/sched/topology.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index ee9eed8470ba..85b46ba594a3 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -471,6 +471,20 @@ DEFINE_PER_CPU(struct sched_domain __rcu *, sd_nohz); static DEFINE_RAW_SPINLOCK(nohz_shared_list_lock); LIST_HEAD(nohz_shared_list); =20 +static void debug_nohz_shared_list_update(void) +{ + struct sched_domain_shared *sds; + int count =3D 0; + + if (!sched_debug()) + return; + + list_for_each_entry(sds, &nohz_shared_list, nohz_list_node) + count++; + + pr_info("%s: %d nohz_shared_list entries found.\n", __func__, count); +} + static int __sds_nohz_idle_alloc_init(struct sched_domain_shared *sds, int= node) { sds->nohz_list_node =3D (struct list_head)LIST_HEAD_INIT(sds->nohz_list_n= ode); @@ -588,6 +602,7 @@ static void update_nohz_domain(int cpu) =20 guard(raw_spinlock)(&nohz_shared_list_lock); list_add_rcu(&sds->nohz_list_node, &nohz_shared_list); + debug_nohz_shared_list_update(); } =20 WARN_ON_ONCE(sd && !sds); @@ -612,8 +627,10 @@ static int sds_delayed_free(struct sched_domain_shared= *sds) if (list_empty(&sds->nohz_list_node)) return 0; =20 - scoped_guard(raw_spinlock_irqsave, &nohz_shared_list_lock) + scoped_guard(raw_spinlock_irqsave, &nohz_shared_list_lock) { list_del_rcu(&sds->nohz_list_node); + debug_nohz_shared_list_update(); + } =20 __nohz_exit_idle_tracking(sds); call_rcu(&sds->rcu, destroy_sched_domain_shared_rcu); --=20 2.34.1