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[24.6.151.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-309f782d07dsm7503407a91.32.2025.04.28.10.39.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Apr 2025 10:39:54 -0700 (PDT) Date: Mon, 28 Apr 2025 10:39:52 -0700 From: Joe Damato To: Willem de Bruijn Cc: Martin Karsten , Samiullah Khawaja , Jakub Kicinski , "David S . Miller" , Eric Dumazet , Paolo Abeni , almasrymina@google.com, willemb@google.com, netdev@vger.kernel.org Subject: Re: [PATCH net-next v5 0/4] Add support to do threaded napi busy poll Message-ID: Mail-Followup-To: Joe Damato , Willem de Bruijn , Martin Karsten , Samiullah Khawaja , Jakub Kicinski , "David S . Miller" , Eric Dumazet , Paolo Abeni , almasrymina@google.com, willemb@google.com, netdev@vger.kernel.org References: <20250424200222.2602990-1-skhawaja@google.com> <52e7cf72-6655-49ed-984c-44bd1ecb0d95@uwaterloo.ca> <680fb23bb1953_23f881294d9@willemb.c.googlers.com.notmuch> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <680fb23bb1953_23f881294d9@willemb.c.googlers.com.notmuch> On Mon, Apr 28, 2025 at 12:52:11PM -0400, Willem de Bruijn wrote: > Martin Karsten wrote: > > On 2025-04-24 16:02, Samiullah Khawaja wrote: > Ack on documentation of the pros/cons. In my mind this includes documenting CPU usage which I know is considered as "non-goal" of this series. It can be a "non-goal" but it is still very relevant to the conversation and documentation. > There is also a functional argument for this feature. It brings > parity with userspace network stacks like DPDK and Google's SNAP [1]. > These also run packet (and L4+) network processing on dedicated cores, > and by default do so in polling mode. An XDP plane currently lacks > this well understood configuration. This brings it closer to parity. It would be good if this could also be included in the cover letter, I think, possibly with example use cases. > Users of such advanced environments can be expected to be well > familiar with the cost of polling. The cost/benefit can be debated > and benchmarked for individual applications. But there clearly are > active uses for polling, so I think it should be an operating system > facility. You mention users of advanced environments, but I think it's important to consider the average user who is not necessarily a kernel programmer. Will that user understand that not all apps support this? Or will they think that they can simply run a few YNL commands burning CPUs at 100% for apps that don't even support this thinking they are making their networking faster? I think providing a mechanism to burn CPU cores at 100% CPU by enabling threaded busy poll has serious consequences on power consumption, cooling requirements, and, errr, earth. I don't think it's a decision to be taken lightly.