netdev - Re: [RFC PATCH 07/11] GENEVE: Add option to mangle IP IDs on inner headers when using TSO

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Date:	Sat, 09 Apr 2016 11:02:28 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	Jesse Gross <jesse@...nel.org>,
	Alexander Duyck <aduyck@...antis.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Tom Herbert <tom@...bertland.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [RFC PATCH 07/11] GENEVE: Add option to mangle IP IDs on inner
 headers when using TSO

On Sat, 2016-04-09 at 10:36 -0700, Alexander Duyck wrote:

> For next version I plan to include a check in netif_skb_features that
> will clear NETIF_F_TSO_MANGLEID if the DF bit is not set.

So it looks like we slowly but surely make the whole stack damn slow, to
support some extra features.

How many instructions are needed nowadays for netif_skb_features()
alone ?

More than 120 if I am not mistaken, if we count fast path in
skb_network_protocol()

Note: I have a patch to remove the gso_min_segs thing, currently unused.

2 instructions saved ! Woo-hoo !