netdev - Re: [PATCH net-next 2/2] udp: Reset flow table for flows over unconnected sockets

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Message-ID: <1414526398.631.23.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 28 Oct 2014 12:59:58 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 2/2] udp: Reset flow table for flows over
 unconnected sockets

On Tue, 2014-10-28 at 12:07 -0700, Tom Herbert wrote:

> As I said, for some applications (like DNS which I suspect you're
> basically emulating) it is infeasible to size the table. Try disabling
> RFS for your test.

Well, we already did experiments.

- DNS servers are using kernel bypass.
  Damn faster than SO_REUSEPORT on UDP anyway (Ying Cai is working on
this problem, since QUIC does not yet use kernel bypass and wants
FQ/pacing)

- Disable RFS for non TCP flows.

- Or have separate hash tables for TCP/UDP (slightly same effect, as UDP
table is mostly empty in our case)


Disabling RFS is the on/off behavior you seem to push, nice for
benchmarks without hassle.

I will no longer comment on this thread, it appears we disagree and wont
find an agreement.


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