From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EEAF027707; Tue, 16 Jun 2026 00:25:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781569537; cv=none; b=VdRFxLAsavt0G/4QCOUjESNNjpNoS7Ilsbti56hvUGIzBC+nGXCwEmKBF4Y5uQG1yhy5WafmwhZ3wzODqZ3sg3ZHPvD6NijkU3nNMpyLq+BsuGg7EJtrt9J5eO23SuE0TaaD0MTjgPdMTm69rtyWGz4HUosf3KA5Dda3H9fQ9Kk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781569537; c=relaxed/simple; bh=CWFSTFYTiBH76MJ3gjOj6t9+K4Ep3BVEdPwrbvarmng=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=DH9VVYKrKTMPV6K6UEZpQnkjUn6WNKkpsxLyvT/j6sNrjwEsJFJRB5zHezzyhwRVqLVyoN55TjVYNTN2Tw0qXPkslziiTkP8LOT6CZXLJzVTnibq2j+sGV8uI3iaXFgYgfLgiGOze3KzBdTAM5ZHEh0vDMaR4TGjvNjzfuHq6z8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YD2garaE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YD2garaE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5D211F000E9; Tue, 16 Jun 2026 00:25:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781569536; bh=hH9/51g//fMBZa4WquaIwRZMdG5lN0iHPMy6YWWkEkY=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=YD2garaEL559AP5FR7kdfCzIspY2D6tCIEctRlILjopg10F0/GTT+kDRVQgKPNi4i jOlOMhi15o646GxtKpw9p7pQgqrnlLwIHsb0IMt+9MGV0PBbZzUNCiRmRInpXpfJ2u /Qev49XJSvZwsrO6EVbpH64sHbbEkzDu/NlfrK+nMzqJUuLfKYdFKj6cyaigGrIdax RSPiK5jWhzmxwddBDsu69spWt5R4BnX4+emEvw5PAZXMADovD0nxMIdor0Xkxcy9mV rI5Ic367l98uI0FcSWn7K98eh/GbqGxjvPq3W8SZmWVnQrOLS4Hwxsi+DqaGMbjuaO e3v3HJXZKXDSw== Date: Mon, 15 Jun 2026 17:25:35 -0700 From: Jakub Kicinski To: Luigi Rizzo Cc: rizzo.unipi@gmail.com, m.szyprowski@samsung.com, robin.murphy@arm.com, willemb@google.com, kuniyu@google.com, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, gregkh@linuxfoundation.org, rafael@kernel.org, akpm@linux-foundation.org, david@kernel.org, netdev@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux.dev, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] swiotlb: avoid double copy with swiotlb on tx socket Message-ID: <20260615172535.080cf94f@kernel.org> In-Reply-To: <20260615234220.3946885-1-lrizzo@google.com> References: <20260615234220.3946885-1-lrizzo@google.com> 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 Mon, 15 Jun 2026 23:42:20 +0000 Luigi Rizzo wrote: > The use of swiotlb causes an extra data copy on I/O. For tx sockets, > especially with greedy senders, this has a high chance of happening in > the softirq handler for tx network interrupts, creating a significant > performance bottleneck. What's the use case? I associate swiotlb with debug / testing mostly, so it'd be useful for people like me to explain why you care. BTW net-next is closed: https://netdev.bots.linux.dev/net-next.html