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Thu, 03 Oct 2024 16:29:38 -0700 (PDT) Date: Thu, 3 Oct 2024 16:29:37 -0700 From: Stanislav Fomichev To: Joe Damato Message-ID: References: <20241001235302.57609-1-jdamato@fastly.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241001235302.57609-1-jdamato@fastly.com> X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1727998179; x=1728602979; darn=lists.osuosl.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=zJJfYTsJBD1YUpbtaYyu99p9PsYf+XDP7HfTuVlkPL0=; b=Gp92z8STeLn2/MlxfCGVYiDmCk0IrgtQCBR5p3+O9/jLdoAitYwkaOfKngnvSpRq/6 Ugp8cQbABBGphzi670gVq10+jT/+Fm+epDVKNbPhBgG3F9kgdQufyD7PrmnhUseZ4osh LHnbv8cadBy3ze/Pda7ozGFke9mRfGBMeCW9FuUa2jbB4weA5iqH0/r8q4H7ICPvfj9H Ys6vJHjFE75rzB1/kzeWhjrCA2rztQErepHjT3RHrbPKdYHC8/ZVGlYpRmCx+uIEeEDS vowjkmI2pp9EVztXUpWFi5vFSaJRNRi6WiyU0HrEYyHluWx91tqN5RZ1MxLckMRjYGDa 8n7w== X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dmarc=pass (p=none dis=none) header.from=gmail.com X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20230601 header.b=Gp92z8ST Subject: Re: [Intel-wired-lan] [RFC net-next v4 0/9] Add support for per-NAPI config via netlink X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "open list:DOCUMENTATION" , mkarsten@uwaterloo.ca, Sebastian Andrzej Siewior , bjorn@rivosinc.com, Eric Dumazet , Tony Nguyen , Daniel Jurgens , Breno Leitao , Mina Almasry , Xuan Zhuo , willemdebruijn.kernel@gmail.com, Donald Hunter , amritha.nambiar@intel.com, Jonathan Corbet , "open list:MELLANOX MLX4 core VPI driver" , Przemek Kitszel , sdf@fomichev.me, "moderated list:INTEL ETHERNET DRIVERS" , Jakub Kicinski , Paolo Abeni , Lorenzo Bianconi , Jiri Pirko , Jesper Dangaard Brouer , Johannes Berg , Michael Chan , skhawaja@google.com, Kory Maincent , Leon Romanovsky , netdev@vger.kernel.org, David Ahern , open list , Tariq Toukan , Alexander Lobakin , sridhar.samudrala@intel.com, Saeed Mahameed , "David S. Miller" Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" On 10/01, Joe Damato wrote: > Greetings: > > Welcome to RFC v4. > > Very important and significant changes have been made since RFC v3 [1], > please see the changelog below for details. > > A couple important call outs for this revision for reviewers: > > 1. idpf embeds a napi_struct in an internal data structure and > includes an assertion on the size of napi_struct. The maintainers > have stated that they think anyone touching napi_struct should update > the assertion [2], so I've done this in patch 3. > > Even though the assertion has been updated, I've given the > cacheline placement of napi_struct within idpf's internals no > thought or consideration. > > Would appreciate other opinions on this; I think idpf should be > fixed. It seems unreasonable to me that anyone changing the size of > a struct in the core should need to think about cachelines in idpf. [..] > 2. This revision seems to work (see below for a full walk through). Is > this the behavior we want? Am I missing some use case or some > behavioral thing other folks need? The walk through looks good! > 3. Re a previous point made by Stanislav regarding "taking over a NAPI > ID" when the channel count changes: mlx5 seems to call napi_disable > followed by netif_napi_del for the old queues and then calls > napi_enable for the new ones. In this RFC, the NAPI ID generation > is deferred to napi_enable. This means we won't end up with two of > the same NAPI IDs added to the hash at the same time (I am pretty > sure). [..] > Can we assume all drivers will napi_disable the old queues before > napi_enable the new ones? If yes, we might not need to worry about > a NAPI ID takeover function. With the explicit driver opt-in via netif_napi_add_config, this shouldn't matter? When somebody gets to converting the drivers that don't follow this common pattern they'll have to solve the takeover part :-)