From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08FC6C3F2D8 for ; Mon, 2 Mar 2020 19:30:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC54A21D56 for ; Mon, 2 Mar 2020 19:30:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727716AbgCBTaA (ORCPT ); Mon, 2 Mar 2020 14:30:00 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:52702 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727672AbgCBT37 (ORCPT ); Mon, 2 Mar 2020 14:29:59 -0500 Received: from localhost (unknown [IPv6:2601:601:9f00:477::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id E36221475D52E; Mon, 2 Mar 2020 11:29:58 -0800 (PST) Date: Mon, 02 Mar 2020 11:29:58 -0800 (PST) Message-Id: <20200302.112958.1038288292834637833.davem@davemloft.net> To: brouer@redhat.com Cc: netdev@vger.kernel.org, ilias.apalodimas@linaro.org, lorenzo@kernel.org, dsahern@gmail.com, toke@toke.dk, saeedm@mellanox.com, tariqt@mellanox.com, kuba@kernel.org, andrew@lunn.ch, thomas.petazzoni@bootlin.com Subject: Re: [net-next PATCH] mvneta: add XDP ethtool errors stats for TX to driver From: David Miller In-Reply-To: <158315678810.1983667.11239367181663328821.stgit@firesoul> References: <158315678810.1983667.11239367181663328821.stgit@firesoul> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Mon, 02 Mar 2020 11:29:59 -0800 (PST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Jesper Dangaard Brouer Date: Mon, 02 Mar 2020 14:46:28 +0100 > Adding ethtool stats for when XDP transmitted packets overrun the TX > queue. This is recorded separately for XDP_TX and ndo_xdp_xmit. This > is an important aid for troubleshooting XDP based setups. > > It is currently a known weakness and property of XDP that there isn't > any push-back or congestion feedback when transmitting frames via XDP. > It's easy to realise when redirecting from a higher speed link into a > slower speed link, or simply two ingress links into a single egress. > The situation can also happen when Ethernet flow control is active. > > For testing the patch and provoking the situation to occur on my > Espressobin board, I configured the TX-queue to be smaller (434) than > RX-queue (512) and overload network with large MTU size frames (as a > larger frame takes longer to transmit). > > Hopefully the upcoming XDP TX hook can be extended to provide insight > into these TX queue overflows, to allow programmable adaptation > strategies. > > Signed-off-by: Jesper Dangaard Brouer Applied, thanks Jesper.