netdev - Re: [RFC] Kernel unaligned access at __skb_flow

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Message-ID: <1454285094.7627.149.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Sun, 31 Jan 2016 16:04:54 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <tom@...bertland.com>
Cc:	Sowmini Varadhan <sowmini.varadhan@...cle.com>,
	Michael Dalton <mwdalton@...gle.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [RFC] Kernel unaligned access at __skb_flow_dissect

On Sun, 2016-01-31 at 14:13 -0800, Tom Herbert wrote:

> Neither is GRE enabled by default in Linux and it is not a typical
> case. So that patch is an optimization for a very narrow use case that
> impacts the core data path for everyone. Please at least consider
> making it configurable.

No idea why it should be configurable, by adding yet another
conditional.

Pulling all headers at once is faster than pulling in GRO slow path, or
if GRO is disabled in pskb_may_pull() slow path.

It seems we need to fix flow dissector anyway.

Note: This path is only taken in non native traffic, in case you missed
this.

Regular IP+TCP or IP+UDP does not use it.