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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ppp@vger.kernel.org Subject: Re: [RFC PATCH net-next] net: ppp: convert to IFF_NO_QUEUE In-Reply-To: <20241104115004.GC2118587@kernel.org> References: <20241029103656.2151-1-dqfext@gmail.com> <20241104115004.GC2118587@kernel.org> X-Clacks-Overhead: GNU Terry Pratchett Date: Tue, 05 Nov 2024 12:47:27 +0100 Message-ID: <87pln99a28.fsf@toke.dk> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Simon Horman writes: > + Toke > > On Tue, Oct 29, 2024 at 06:36:56PM +0800, Qingfang Deng wrote: >> When testing the parallel TX performance of a single PPPoE interface >> over a 2.5GbE link with multiple hardware queues, the throughput could >> not exceed 1.9Gbps, even with low CPU usage. >> >> This issue arises because the PPP interface is registered with a single >> queue and a tx_queue_len of 3. This default behavior dates back to Linux >> 2.3.13, which was suitable for slower serial ports. However, in modern >> devices with multiple processors and hardware queues, this configuration >> can lead to congestion. >> >> For PPPoE/PPTP, the lower interface should handle qdisc, so we need to >> set IFF_NO_QUEUE. For PPP over a serial port, we don't benefit from a >> qdisc with such a short TX queue, so handling TX queueing in the driver >> and setting IFF_NO_QUEUE is more effective. >> >> With this change, PPPoE interfaces can now fully saturate a 2.5GbE link. >> >> Signed-off-by: Qingfang Deng > > Hi Toke, > > I'm wondering if you could offer an opinion on this. Hi Simon Thanks for bringing this to my attention; I'll reply to the parent directly :) -Toke