From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 42BA4145B3E for ; Sat, 8 Nov 2025 01:11:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762564267; cv=none; b=mF92NB4l3jprQdw/Y3duPthLB+Npzj4H+gQEHSFh27kI7V36vrKpicIql9o7XrH/3UZHAD1MUF09B3tbflcVVHDkRKFwv/UScUUTD7A8ats2jg053FX0YPEN7JEo+OUhducozrYupOrsdoXK0MFZeX2a7O77dFzUuHHh4AYRIdA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762564267; c=relaxed/simple; bh=vKvPEc0OL56xvPcMsxJFQrmcCo4e6Q05X9tUYOSx5KQ=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=qa8JOLNProcVWdFwsSomtKsuCEyAe/gq6n1xK4wiiTR213u5Ril0AbHuRvgtSL996Fkkzs/okR9tEo//Bba0NnHFJA0xISB6Oy0jgAz5UBDITrBYMnM7d+IGll6y+XMeMXlw1/VGn5sfbbD+FBiDU6sgpzXkcvNfKMM9bRQnJkg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=owVNnjE7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="owVNnjE7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6BC35C4CEF7; Sat, 8 Nov 2025 01:11:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762564264; bh=vKvPEc0OL56xvPcMsxJFQrmcCo4e6Q05X9tUYOSx5KQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=owVNnjE7rpsR/fXVy5i3r/TrRDPynfRnlN1NADbVrhl52cS7clwQNTMMG1PYBZwd6 zsN/QkKp8g1wByCaab8YVZtJ1w/idgxBkfjBShJJDFjUwCll9g4fMp9a7E0EI5CY9l hqx5OdAayvLn/LCYNF2xJ08qSVXJxter+bNwOI3A0h9EyQQBpILa/PhjzqBGgs7I0r jZ09zNxBF8kj4s1sBU+w64/djiAKf+YWm47XsO2LGLr7gX9WXQqHQSkVTBJpn6MLmN PuknKC7EFvyrraIzHidgPob8im5tyr7Acns0XfzuwqTYPkWuYuKC7PbX4LwwxwIcxZ 0Rt7Y1X3QxvTA== Date: Fri, 7 Nov 2025 17:11:03 -0800 From: Jakub Kicinski To: Lorenzo Bianconi Cc: Eric Dumazet , Andrew Lunn , "David S. Miller" , Paolo Abeni , linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, netdev@vger.kernel.org Subject: Re: [PATCH net-next] net: airoha: Add TCP LRO support Message-ID: <20251107171103.2ecda810@kernel.org> In-Reply-To: References: <20250610-airoha-eth-lro-v1-1-3b128c407fd8@kernel.org> <20250611173626.54f2cf58@kernel.org> <20250612155721.4bb76ab1@kernel.org> <20251031111641.08471c44@kernel.org> 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-Transfer-Encoding: 7bit On Fri, 7 Nov 2025 14:30:02 +0100 Lorenzo Bianconi wrote: > > On Fri, 31 Oct 2025 09:42:15 +0100 Lorenzo Bianconi wrote: > > > Sorry for the late reply about this item. > > > I carried out some comparison tests between GRO-only and GRO+LRO with order-2 > > > pages [0]. The system is using a 2.5Gbps link. The device is receiving a single TCP > > > stream. MTU is set to 1500B. > > > > > > - GRO only: ~1.6Gbps > > > - GRO+LRO (order-2 pages): ~2.1Gbps > > > > > > In both cases we can't reach the line-rate. Do you think the difference can justify > > > the hw LRO support? Thanks in advance. > > > > > > [0] the hw LRO requires contiguous memory pages to work. I reduced the size to > > > order-2 from order-5 (original implementation). > > > > I think we're mostly advising about real world implications of > > the approach rather than nacking. I can't say for sure if potentially > > terrible skb->len/skb->truesize ratio will matter for a router > > application. Maybe not. > > > > BTW is the device doing header-data split or the LRO frame has headers > > and payload in a single buffer? > > According to my understanding the hw LRO is limited to a single order-x page > containing both the headers and the payload (the hw LRO module is not capable > of splitting the aggregated TCP segment over multiple pages). > What we could do is disable hw LRO by default and feed hw rx queues with > order-0 pages (current implementation). If the user enables hw LRO, we will > free order-0 pages linked to the rx DMA descriptors and allocate order-x pages > (e.g. order-2) for hw LRO queues. Disabling hw LRO will switch back to order-0 > pages. Are all packets LRO-sized when it's enabled? What you describe is definitely good, bur I was wondering if we can also use rx-buf-len to let user select the size / order of the LRO buffers. But the definition of rx-buf-len is that it's for _all_ rx buffers on given queue. We'd probably need a new param if the pages are just for lro