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, 9 Apr 2016 11:32:09 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Eric Dumazet <eric.dumazet@...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, Apr 9, 2016 at 11:02 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> 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 !

I was planning to drop the checks for TSO_MANGLEID and GSO_PARTIAL in
a if statment based on skb_is_gso() since I had both GSO_PARTIAL to
check for as well.

- Alex