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Sun, 1 Dec 2024 18:42:45 +0000 Date: Sun, 1 Dec 2024 18:42:44 +0000 (GMT) From: Aaron Tomlin To: oleg@redhat.com, frederic@kernel.org, peterz@infradead.org cc: atomlin@atomlin.com, nick.lange@gmail.com, seun.ewulomi@gmail.com, linux-kernel@vger.kernel.org Subject: [RFC PATCH 0/1] sched/isolation: Warn when maxcpus= is specified with nohz_full= or isolcpus= Message-ID: Content-Type: multipart/mixed; boundary="-1463799552-1067086594-1733078564=:8619" X-ClientProxiedBy: LO4P123CA0176.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:18a::19) To CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) 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: CWLP123MB3523:EE_|LO2P123MB7148:EE_ X-MS-Office365-Filtering-Correlation-Id: 11d7c938-1d76-4c5b-9780-08dd1237f1d6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|366016; 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charset=US-ASCII Hi Oleg, Frederic, Peter, I have seen a case where maxcpus=1 and e.g. nohz_full=1,3-31, was used to force the CPU affinity of certain unbound or non CPU-specific kernel threads at boot-time. Albeit, since commit 9cc5b8656892a ("isolcpus: Affine unbound kernel threads to housekeeping cpus") this is handled entirely via nohz_full=. I thought it might be worth adding a warning. Aaron Tomlin (1): sched/isolation: Warn when maxcpus= is specified with nohz_full= or isolcpus= kernel/sched/isolation.c | 2 ++ 1 file changed, 2 insertions(+) -- 2.47.1 -- Aaron Tomlin ---1463799552-1067086594-1733078564=:8619 Content-Type: text/plain; charset=US-ASCII; name=0001-sched-isolation-Warn-when-maxcpus-is-specified-with-.patch Content-Transfer-Encoding: BASE64 Content-ID: Content-Description: Content-Disposition: attachment; filename=0001-sched-isolation-Warn-when-maxcpus-is-specified-with-.patch RnJvbSA5ZDgyZWI5ZjljMDAxMDAyNTA0N2M0NTc1NGVjODFjMzgzMjU0N2U0IE1vbiBTZXAgMTcg MDA6MDA6MDAgMjAwMQ0KRnJvbTogQWFyb24gVG9tbGluIDxhdG9tbGluQGF0b21saW4uY29tPg0K RGF0ZTogU2F0LCAzMCBOb3YgMjAyNCAyMzozMTozOSArMDAwMA0KU3ViamVjdDogW1JGQyBQQVRD SCAxLzFdIHNjaGVkL2lzb2xhdGlvbjogV2FybiB3aGVuIG1heGNwdXM9IGlzIHNwZWNpZmllZCB3 aXRoDQogbm9oel9mdWxsPSBvciBpc29sY3B1cz0NCg0KSW4gdGhlIGNvbnRleHQgb2YgaG91c2Vr ZWVwaW5nX3NldHVwKCksIHRoZSB1c2Ugb2YgbWF4Y3B1cz0gZG9lcyBub3QNCmRpY3RhdGUgaG93 IHRoZSBob3VzZWtlZXBpbmcgQ1BVIG1hc2sgaXMgYnVpbHQgaS5lLiBvbmx5IHRoZSAicG9zc2li bGUiDQpDUFUgbWFzayBhbmQgbm9uLWhvdXNla2VlcGluZyBDUFUgbWFzayBpcyBjb25zaWRlcmVk LiBJbmRlZWQgdGhlDQpwb3NzaWJsZSBDUFUgbWFzayBpcyBpbmRpY2F0aXZlIG9mIHRoZSBDUFUo cykgdGhhdCBjYW4gYmUgYnJvdWdodCBvbmxpbmUNCmlmIHRoZXkgYXJlIHBoeXNpY2FsIHByZXNl bnQuDQoNClNvbWUgY3VzdG9tZXJzIGluIHRoZSBwYXN0IGhhdmUgdXNlZCBtYXhjcHVzPTEgZS5n LiB3aXRoDQpub2h6X2Z1bGw9MSwzLTMxLCB0byBmb3JjZSB0aGUgQ1BVIGFmZmluaXR5IG9mIGNl cnRhaW4gdW5ib3VuZCBvciBub24NCkNQVS1zcGVjaWZpYyBrZXJuZWwgdGhyZWFkcyBhdCBib290 LXRpbWUuIEFsYmVpdCwgc2luY2UgY29tbWl0DQo5Y2M1Yjg2NTY4OTJhICgiaXNvbGNwdXM6IEFm ZmluZSB1bmJvdW5kIGtlcm5lbCB0aHJlYWRzIHRvIGhvdXNla2VlcGluZw0KY3B1cyIpIHRoaXMg aXMgaGFuZGxlZCBlbnRpcmVseSB2aWEgbm9oel9mdWxsPS4NCg0KVGhpcyBwYXRjaCBhZGRzIGEg c2ltcGxlIHdhcm5pbmcgd2hlbiBtYXhjcHVzPSBhbmQgbm9oel9mdWxsPSBvcg0KaXNvbGNwdXM9 IGlzIHNwZWNpZmllZC4gSG93ZXZlciwgc2luY2UgY29tbWl0IDI1N2JmODlkODQxMjENCigic2No ZWQvaXNvbGF0aW9uOiBGaXggYm9vdCBjcmFzaCB3aGVuIG1heGNwdXMgPCBmaXJzdCBob3VzZWtl ZXBpbmcNCkNQVSIpIG1heGNwdXM9MSBhbmQgYW4gdW5zdWl0YWJsZSBub2h6X2Z1bGw9IHJlYWRp bmcgaXMgaGFuZGxlZA0KYXBwcm9wcmlhdGVseSBub3cuDQoNClNpZ25lZC1vZmYtYnk6IEFhcm9u IFRvbWxpbiA8YXRvbWxpbkBhdG9tbGluLmNvbT4NCi0tLQ0KIGtlcm5lbC9zY2hlZC9pc29sYXRp b24uYyB8IDIgKysNCiAxIGZpbGUgY2hhbmdlZCwgMiBpbnNlcnRpb25zKCspDQoNCmRpZmYgLS1n aXQgYS9rZXJuZWwvc2NoZWQvaXNvbGF0aW9uLmMgYi9rZXJuZWwvc2NoZWQvaXNvbGF0aW9uLmMN CmluZGV4IDU4OTFlNzE1ZjAwZC4uMjdjZGM3MTFkY2Y1IDEwMDY0NA0KLS0tIGEva2VybmVsL3Nj aGVkL2lzb2xhdGlvbi5jDQorKysgYi9rZXJuZWwvc2NoZWQvaXNvbGF0aW9uLmMNCkBAIC0xMzgs NiArMTM4LDggQEAgc3RhdGljIGludCBfX2luaXQgaG91c2VrZWVwaW5nX3NldHVwKGNoYXIgKnN0 ciwgdW5zaWduZWQgbG9uZyBmbGFncykNCiAJYWxsb2NfYm9vdG1lbV9jcHVtYXNrX3ZhcigmaG91 c2VrZWVwaW5nX3N0YWdpbmcpOw0KIAljcHVtYXNrX2FuZG5vdChob3VzZWtlZXBpbmdfc3RhZ2lu ZywNCiAJCSAgICAgICBjcHVfcG9zc2libGVfbWFzaywgbm9uX2hvdXNla2VlcGluZ19tYXNrKTsN CisJaWYgKHNldHVwX21heF9jcHVzICE9IE5SX0NQVVMpDQorCQlwcl93YXJuKCJIb3VzZWtlZXBp bmc6IG1heGNwdXM9IGhhcyBiZWVuIHNwZWNpZmllZCB0b29cbiIpOw0KIA0KIAlmaXJzdF9jcHUg PSBjcHVtYXNrX2ZpcnN0X2FuZChjcHVfcHJlc2VudF9tYXNrLCBob3VzZWtlZXBpbmdfc3RhZ2lu Zyk7DQogCWlmIChmaXJzdF9jcHUgPj0gbnJfY3B1X2lkcyB8fCBmaXJzdF9jcHUgPj0gc2V0dXBf bWF4X2NwdXMpIHsNCi0tIA0KMi40Ny4xDQoNCg== ---1463799552-1067086594-1733078564=:8619--