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 97AE82222CA for ; Mon, 21 Apr 2025 22:28:35 +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=1745274515; cv=none; b=N7qvfuKHOvDu2rA2Dzso2n2Ts0e2X1dz5uxifDZysw1CqJ47XE7vR3FT9zGOZaHW9cn/bkjgq/YRWo8Yb1Sk6jpW/gBejlfvFYbL/uK3UE52FQn4g9QLpKCglXI4Kwm3EbXOJzk3d+zuDUW0Ej1nUFcHbB5MhdY3P1XOsN3Izv0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745274515; c=relaxed/simple; bh=T4fleFadU9HUdchSN5jF1GlhLbSMoFcXuQqhjZTDfcQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jeTfSMce4mDXjFUC08n+jxf7VjmtlK63yV/ThAmZFSWQC8nxsIoA1BsITZ6k05Lz2fl+SrhB48+bwJZU4Exe7ppMSqzVnUJfhctIFOFcPYfwaKddQ11EwV/JhG1fg5pb596RnSzGA6Im+0BpA0bCWEMZ+9fHJy1o07cQb2q4XkY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qZgQiGL+; 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="qZgQiGL+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9EF7DC4CEEE; Mon, 21 Apr 2025 22:28:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745274515; bh=T4fleFadU9HUdchSN5jF1GlhLbSMoFcXuQqhjZTDfcQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qZgQiGL+epgP1/nbeQXMPMjPp27OYV9Tdbd+9LDPi5qswLab+6x6SCxuqWDJz3Ib7 I86qe49WjgPEBJGwWRRJRNlMp1n1u6KQeIbXjxNO3ZnBrOSuYIUkXe1Zjtrf/WfqtD 0640Zj3tPhzek/CszYBDp5x1poej/scplGA+Q365Fw2uTcusjzHewcar4wY42HcGir ZXUeOPtCaepnwZiiffkzn9DnOXDY+ExVoQ1/88l7St1a85hV7u064IOTDKOKyqWuIb eY5nYWe76PSIO3GqT2YZ257vW8yWx4bG31CCffw8zXacfXK3g6TSmA6sojl17mSGZQ FR51Jc70QpLJg== From: Jakub Kicinski To: davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, donald.hunter@gmail.com, sdf@fomichev.me, almasrymina@google.com, dw@davidwei.uk, asml.silence@gmail.com, ap420073@gmail.com, jdamato@fastly.com, dtatulea@nvidia.com, michael.chan@broadcom.com, Jakub Kicinski Subject: [RFC net-next 01/22] docs: ethtool: document that rx_buf_len must control payload lengths Date: Mon, 21 Apr 2025 15:28:06 -0700 Message-ID: <20250421222827.283737-2-kuba@kernel.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250421222827.283737-1-kuba@kernel.org> References: <20250421222827.283737-1-kuba@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Document the semantics of the rx_buf_len ethtool ring param. Clarify its meaning in case of HDS, where driver may have two separate buffer pools. The various zero-copy TCP Rx schemes we have suffer from memory management overhead. Specifically applications aren't too impressed with the number of 4kB buffers they have to juggle. Zero-copy TCP makes most sense with larger memory transfers so using 16kB or 32kB buffers (with the help of HW-GRO) feels more natural. Signed-off-by: Jakub Kicinski --- Documentation/networking/ethtool-netlink.rst | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst index b6e9af4d0f1b..eaa9c17a3cb1 100644 --- a/Documentation/networking/ethtool-netlink.rst +++ b/Documentation/networking/ethtool-netlink.rst @@ -957,7 +957,6 @@ Kernel checks that requested ring sizes do not exceed limits reported by driver. Driver may impose additional constraints and may not support all attributes. - ``ETHTOOL_A_RINGS_CQE_SIZE`` specifies the completion queue event size. Completion queue events (CQE) are the events posted by NIC to indicate the completion status of a packet when the packet is sent (like send success or @@ -971,6 +970,11 @@ completion queue size can be adjusted in the driver if CQE size is modified. header / data split feature. If a received packet size is larger than this threshold value, header and data will be split. +``ETHTOOL_A_RINGS_RX_BUF_LEN`` controls the size of the buffer chunks driver +uses to receive packets. If the device uses different memory polls for headers +and payload this setting may control the size of the header buffers but must +control the size of the payload buffers. + CHANNELS_GET ============ -- 2.49.0