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Date: Fri, 29 Nov 2019 17:07:20 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: David Laight <David.Laight@...LAB.COM>, 'Paolo Abeni' <pabeni@...hat.com>, Jesper Dangaard Brouer <brouer@...hat.com> Cc: 'Marek Majkowski' <marek@...udflare.com>, linux-kernel <linux-kernel@...r.kernel.org>, network dev <netdev@...r.kernel.org>, kernel-team <kernel-team@...udflare.com> Subject: Re: epoll_wait() performance On 11/28/19 2:17 AM, David Laight wrote: > From: Eric Dumazet >> Sent: 27 November 2019 17:47 > ... >> A QUIC server handles hundred of thousands of ' UDP flows' all using only one UDP socket >> per cpu. >> >> This is really the only way to scale, and does not need kernel changes to efficiently >> organize millions of UDP sockets (huge memory footprint even if we get right how >> we manage them) >> >> Given that UDP has no state, there is really no point trying to have one UDP >> socket per flow, and having to deal with epoll()/poll() overhead. > > How can you do that when all the UDP flows have different destination port numbers? > These are message flows not idempotent requests. > I don't really want to collect the packets before they've been processed by IP. > > I could write a driver that uses kernel udp sockets to generate a single message queue > than can be efficiently processed from userspace - but it is a faff compiling it for > the systems kernel version. Well if destinations ports are not under your control, you also could use AF_PACKET sockets, no need for 'UDP sockets' to receive UDP traffic, especially it the rate is small.
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