netdev - Re: [PATCH net-next 2/3] udp: use a separate rx queue for packet reception

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Message-ID: <1494864649.6465.1.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 15 May 2017 09:10:49 -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>
Subject: Re: [PATCH net-next 2/3] udp: use a separate rx queue for packet
 reception

On Mon, 2017-05-15 at 11:01 +0200, Paolo Abeni wrote:
> under udp flood the sk_receive_queue spinlock is heavily contended.
> This patch try to reduce the contention on such lock adding a
> second receive queue to the udp sockets; recvmsg() looks first
> in such queue and, only if empty, tries to fetch the data from
> sk_receive_queue. The latter is spliced into the newly added
> queue every time the receive path has to acquire the
> sk_receive_queue lock.
> 
> The accounting of forward allocated memory is still protected with
> the sk_receive_queue lock, so udp_rmem_release() needs to acquire
> both locks when the forward deficit is flushed.
> 
> On specific scenarios we can end up acquiring and releasing the
> sk_receive_queue lock multiple times; that will be covered by
> the next patch
> 
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---

Very nice, thanks for working on this Paolo.

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