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[2003:ea:8f2f:3200:9c37:6397:15a9:b6d2]) by smtp.googlemail.com with ESMTPSA id z9sm4444554wmf.21.2019.08.16.12.12.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Aug 2019 12:12:56 -0700 (PDT) Subject: Re: r8169: Performance regression and latency instability To: =?UTF-8?Q?Holger_Hoffst=c3=a4tte?= , Eric Dumazet , Juliana Rodrigueiro , netdev@vger.kernel.org References: <72898d5b-9424-0bcd-3d8a-fc2e2dd0dbf1@intra2net.com> <217e3fa9-7782-08c7-1f2b-8dabacaa83f9@gmail.com> <792d3a56-32aa-afee-f2b4-1f867b9cf75f@applied-asynchrony.com> From: Heiner Kallweit Message-ID: <8fa71d82-d309-df38-5924-2275db188b61@gmail.com> Date: Fri, 16 Aug 2019 21:12:49 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <792d3a56-32aa-afee-f2b4-1f867b9cf75f@applied-asynchrony.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 16.08.2019 15:59, Holger Hoffstätte wrote: > On 8/16/19 2:35 PM, Eric Dumazet wrote: > ..snip.. >> I also see this relevant commit : I have no idea why SG would have any relation with TSO. >> >> commit a7eb6a4f2560d5ae64bfac98d79d11378ca2de6c >> Author: Holger Hoffstätte >> Date:   Fri Aug 9 00:02:40 2019 +0200 >> >>      r8169: fix performance issue on RTL8168evl >>           Disabling TSO but leaving SG active results is a significant >>      performance drop. Therefore disable also SG on RTL8168evl. >>      This restores the original performance. >>           Fixes: 93681cd7d94f ("r8169: enable HW csum and TSO") >>      Signed-off-by: Holger Hoffstätte >>      Signed-off-by: Heiner Kallweit >>      Signed-off-by: David S. Miller > > It does not - and admittedly none of this makes sense, but stay with me here. > > The commit 93681cd7d94f to net-next enabled rx/tx HW checksumming and TSO > by default, but disabled TSO for one specific chip revision - the most popular > one, of course. Enabling rx/tx checksums by default while leaving SG on turned > out to be the performance issue (~780 MBit max) that I found & fixed in the > quoted commit. SG *can* be enabled when rx/tx checkusmming is *dis*abled > (I just verified again), we just had to sanitize the new default. > > An alternative strategy could still be to (again?) disable everything by default > and just let people manually enable whatever settings work for their random > chip revision + BIOS combination. I'll let Heiner chime in here. > > Basically these chips are dumpster fires and should not be used for anything > ever, which of course means they are everywhere. > > AFAICT none of this has anything to do with Juliana's problem.. > Indeed, here we're talking about changes in linux-next, and Juliana's issue is with 4.19. However I'd appreciate if Juliana could test with linux-next and different combinations of the NETIF_F_xxx features. I have no immediate idea why the referenced GSO change affects r8169 but not other chips / drivers. > -h > Heiner