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([2a01:e0a:b41:c160:416:9ea1:405b:86ea]) by smtp.gmail.com with ESMTPSA id fc18-20020a05600c525200b003b505d26776sm8853533wmb.5.2022.10.24.05.27.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Oct 2022 05:27:20 -0700 (PDT) Message-ID: <5af190a8-ac35-82a6-b099-e9a817757676@6wind.com> Date: Mon, 24 Oct 2022 14:27:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Reply-To: nicolas.dichtel@6wind.com Subject: Re: [RFE net-next] net: tun: 1000x speed up Content-Language: en-US To: Ilya Maximets , Jakub Kicinski Cc: netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Paolo Abeni , linux-kernel@vger.kernel.org References: <20221021114921.3705550-1-i.maximets@ovn.org> <20221021090756.0ffa65ee@kernel.org> From: Nicolas Dichtel Organization: 6WIND In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 24/10/2022 à 13:56, Ilya Maximets a écrit : > On 10/24/22 11:44, Nicolas Dichtel wrote: >> Le 21/10/2022 à 18:07, Jakub Kicinski a écrit : >>> On Fri, 21 Oct 2022 13:49:21 +0200 Ilya Maximets wrote: >>>> Bump the advertised speed to at least match the veth. 10Gbps also >>>> seems like a more or less fair assumption these days, even though >>>> CPUs can do more. Alternative might be to explicitly report UNKNOWN >>>> and let the application/user decide on a right value for them. >>> >>> UNKOWN would seem more appropriate but at this point someone may depend >>> on the speed being populated so it could cause regressions, I fear :S >> If it is put in a bonding, it may cause some trouble. Maybe worth than >> advertising 10M. > > My thoughts were that changing the number should have a minimal impact > while changing it to not report any number may cause some issues in > applications that doesn't expect that for some reason (not having a > fallback in case reported speed is unknown isn't great, and the argument > can be made that applications should check that, but it's hard to tell > for every application if they actually do that today). > > Bonding is also a good point indeed, since it's even in-kernel user. > > > The speed bump doesn't solve the problem per se. It kind of postpones > the decision, since we will run into the same issue eventually again. > That's why I wanted to discuss that first. > > Though I think that at least unification across virtual devices (tun and > veth) should be a step in a right direction. Just to make it clear, I'm not against aligning speed with veth, I'm only against reporting UNKNOWN. > >> >> Note that this value could be configured with ethtool: >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4e24f2dd516ed > > This is interesting, but it's a bit hard to manage, because in order > to make a decision to bump the speed, application should already know > that this is a tun/tap device. So, there has to be a special case But this should be done by the application which creates this tun interface. Not by the application that uses this information. > implemented in the code that detects the driver and changes the speed > (this is about application that is using the interface, but didn't > create it), but if we already know the driver, then it doesn't make > sense to actually change the speed in many cases as application can > already act accordingly. > > Also, the application may not have permissions to do that (I didn't > check the requirements, but my guess would be at least CAP_NET_ADMIN?). Sure, but the one who creates it, has the right to configure it correctly. It's part of the configuration of the interface. Setting an higher default speed seems to be a workaround to fix an incorrect configuration. And as you said, it will probably be wrong again in a few years ;-) > > For the human user it's still one extra configuration step that they > need to remember to perform. I don't buy this argument. There are already several steps: creating and configuring an interface requires more than one command. Regards, Nicolas