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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, 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 C6FF3C4320A for ; Sat, 21 Aug 2021 09:50:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A6F9760187 for ; Sat, 21 Aug 2021 09:50:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233879AbhHUJve (ORCPT ); Sat, 21 Aug 2021 05:51:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:58706 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233286AbhHUJvb (ORCPT ); Sat, 21 Aug 2021 05:51:31 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2D9A861040; Sat, 21 Aug 2021 09:50:52 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mHNeM-006Lq1-48; Sat, 21 Aug 2021 10:50:50 +0100 Date: Sat, 21 Aug 2021 10:50:41 +0100 Message-ID: <878s0vqg7i.wl-maz@kernel.org> From: Marc Zyngier To: Jakub Kicinski Cc: netdev@vger.kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, Matteo Croce , "David S. Miller" , Eric Dumazet , Giuseppe Cavallaro , Alexandre Torgue Subject: Re: [PATCH net] stmmac: Revert "stmmac: align RX buffers" In-Reply-To: <20210820144610.7576c36a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> References: <20210820183002.457226-1-maz@kernel.org> <20210820144610.7576c36a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kuba@kernel.org, netdev@vger.kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, mcroce@linux.microsoft.com, davem@davemloft.net, eric.dumazet@gmail.com, peppe.cavallaro@st.com, alexandre.torgue@foss.st.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 20 Aug 2021 22:46:10 +0100, Jakub Kicinski wrote: > > On Fri, 20 Aug 2021 19:30:02 +0100 Marc Zyngier wrote: > > This reverts commit a955318fe67e ("stmmac: align RX buffers"), > > which breaks at least one platform (Nvidia Jetson-X1), causing > > packet corruption. This is 100% reproducible, and reverting > > the patch results in a working system again. > > > > Given that it is "only" a performance optimisation, let's > > return to a known working configuration until we can have a > > good understanding of what is happening here. > > Seems reasonable. Hopefully it wont discourage Matteo from revisiting > the optimization. Applied, thanks! That's my hope too. As I pointed out at the end of the towards the end of the discussion I linked to, this buys us time to work out exactly where is the gap in our understanding of the buffer allocation for this particular driver. Once we clearly understand why it fails on some systems and not some others (which on its own could cover a multitude of sins), I'd be glad to see this optimisation brought back in, and I'm willing to help with it. Thanks, M. -- Without deviation from the norm, progress is not possible.