netdev - Re: [PATCH net-next v2 2/2] udp: do fwd memory scheduling on dequeue

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Date:   Fri, 04 Nov 2016 05:38:28 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        linux-nfs@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/2] udp: do fwd memory scheduling on dequeue

On Fri, 2016-11-04 at 11:28 +0100, Paolo Abeni wrote:
> A new argument is added to __skb_recv_datagram to provide
> an explicit skb destructor, invoked under the receive queue
> lock.
> The UDP protocol uses such argument to perform memory
> reclaiming on dequeue, so that the UDP protocol does not
> set anymore skb->desctructor.
> Instead explicit memory reclaiming is performed at close() time and
> when skbs are removed from the receive queue.
> The in kernel UDP protocol users now need to call a
> skb_recv_udp() variant instead of skb_recv_datagram() to
> properly perform memory accounting on dequeue.
> 
> Overall, this allows acquiring only once the receive queue
> lock on dequeue.
> 
> Tested using pktgen with random src port, 64 bytes packet,
> wire-speed on a 10G link as sender and udp_sink as the receiver,
> using an l4 tuple rxhash to stress the contention, and one or more
> udp_sink instances with reuseport.
> 
> nr sinks	vanilla		patched
> 1		440		560
> 3		2150		2300
> 6		3650		3800
> 9		4450		4600
> 12		6250		6450
> 
> v1 -> v2:
>  - do rmem and allocated memory scheduling under the receive lock
>  - do bulk scheduling in first_packet_length() and in udp_destruct_sock()
>  - avoid the typdef for the dequeue callback
> 
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
> @Eric, please add your signed off by when you feel comfortable with the patch
> as you authored some of the code

SGTM, thanks Paolo and Hannes !

Acked-by: Eric Dumazet <edumazet@...gle.com>