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15.21.0406.007; Thu, 17 Sep 2026 15:45:27 +0000 From: "Ionut Nechita (Wind River)" To: atomlin@atomlin.com Cc: axboe@kernel.dk, tglx@kernel.org, mkp@kernel.org, frederic@kernel.org, bigeasy@linutronix.de, corbet@lwn.net, vincent.guittot@linaro.org, mingo@redhat.com, peterz@infradead.org, marco.crivellari@suse.com, neelx@suse.com, linux-doc@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v16 0/9] blk: honor isolcpus configuration Date: Thu, 17 Sep 2026 18:44:51 +0300 Message-ID: <20260917154455.386769-1-ionut.nechita@windriver.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260910164237.500196-1-atomlin@atomlin.com> References: <20260910164237.500196-1-atomlin@atomlin.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: JNAP275CA0052.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:4e::15) To SJ2PR11MB7546.namprd11.prod.outlook.com (2603:10b6:a03:4cc::8) Precedence: bulk X-Mailing-List: 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Just a heads-up that I have picked up v16 and am backporting it to the 6.18 LTS tree so I can exercise the new parameter on our PREEMPT_RT configuration. The goal is to validate the end-to-end behaviour of managed_irq_strict on multiqueue hardware (NVMe and SCSI) with isolated cores, in particular: - managed IRQ affinity and the reserved pre/post vectors staying off the isolated set and confined to housekeeping CPUs; - the blk-mq hotplug guard that refuses to offline the last housekeeping CPU still serving an online isolated core; - queue/vector counts on systems where nr_vectors >= nr_cpus (narrow housekeeping pools, many PFs + NVMe). I will follow up on this thread with results (effective_affinity and blk-mq queue mapping data, plus any backport-specific findings) once testing on 6.18 LTS is complete. On the maintainer question (option 1 vs option 2): from a downstream/product standpoint I favour option 1, keeping "managed_irq_strict" as an explicit opt-in. Leaving the legacy "managed_irq" semantics unchanged avoids a silent behavioural change for existing deployments, while the strict variant gives new users a clear, predictable knob. Thanks for driving this forward. Ionut