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([2a01:aec0:a3fd:7260:9636:62ff:a8fd:5751]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5733becfcc1sm6010876a12.45.2024.05.13.05.33.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 May 2024 05:33:15 -0700 (PDT) Message-ID: Date: Mon, 13 May 2024 14:33:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: ming.lei@redhat.com Cc: benjamin.meier70@gmail.com, hch@lst.de, kbusch@kernel.org, kbusch@meta.com, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, tglx@linutronix.de References: Subject: Re: [PATCH 2/2] nvme-pci: allow unmanaged interrupts Content-Language: en-US From: Benjamin Meier In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240513_053318_560980_0243B882 X-CRM114-Status: GOOD ( 19.57 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org > 'isolcpus=managed_irq' enablement patches are small, and shouldn't be very > hard to backport. I have big respect of kernel code and probably for non-kernel devs it's not so easy:) But yeah, we'll look into this. > > > > be tricky to assign all interrupts to those without a > > performance-penalty. > > > > > > > > Given these requirements, manually specifying interrupt/core assignments > > > > would offer greater flexibility and control over system performance. > > > > Moreover, the proposed code changes appear minimal and have no > > > > impact on existing functionalities. > > > > > > Looks your main concern is performance, but as Keith mentioned, the > > proposed > > > change may degrade nvme perf too: > > > > > > https://lore.kernel.org/linux-nvme/Zj6745UDnwX1BteO@kbusch-mbp.dhcp.thefacebook.com/ > > > > Yes, but for NVMe it's not that critical. The most important point for us is > > to keep them away from our "high-priority" cores. We still wanted to have > > control > > where we run those interrupts, but also because we just did not know the > > "managed_irq" > > option. > > OK, thanks for share the input! > > Now from upstream viewpoint, 'isolcpus=managed_irq' should work for your case, > and seems not necessary to support nvme unmanaged irq for this requirement > at least. Yes, probably that will do it. Personally, I still think it's a nice thing if it's possible to assign interrupts to specific cores, but practically the advantages are likely not that big compared to 'isolcpus=managed_irq'. Thanks for all the explanations