netdev - Re: [PATCH net-next v3 3/4] net: use skb->priority for overloading skb->dropcount and skb->reserved

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Message-ID: <1424783915.5565.74.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 24 Feb 2015 05:18:35 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Eyal Birger <eyal.birger@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Shmulik Ladkani <shmulik.ladkani@...il.com>,
	Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3 3/4] net: use skb->priority for overloading
 skb->dropcount and skb->reserved_tailroom instead of skb->mark

On Tue, 2015-02-24 at 12:10 +0200, Eyal Birger wrote:

> 
> Well, gave it a shot... it looks like several protocol families
> (packet, rxrpc, bluetooth) do not
> have room in skb->cb[] for the dropcount - at least on my 64 bit machine.

No idea how you took a look ?

sizeof(struct packet_skb_cb) == 24  : We have plenty of room ?


bluetooth : Whole struct rxrpc_skb_priv is not used when packet is
stored in receive queue.

We only need bt_cb(skb)->psm & bt_cb(skb)->bdaddr according to
l2cap_skb_msg_name()

An union will be possible.

rxpc is buggy right now anyway, as it reads skb->mark _and_ uses
sock_recv_ts_and_drops(), so skb->mark value is pretty much void.

Note that resend_at field could probably converted into u32. tcp stack
uses same (u32)jiffies trick (tcp_time_stamp)


I never said it was going to be easy ;)


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