netdev - Re: [RFC net-next 2/2] udp: No longer use SLAB_DESTROY_BY

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Message-ID: <20160326015556.GA84340@ast-mbp.thefacebook.com>
Date:	Fri, 25 Mar 2016 18:55:58 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Eric Dumazet <edumazet@...gle.com>
Cc:	"David S . Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Tom Herbert <tom@...bertland.com>
Subject: Re: [RFC net-next 2/2] udp: No longer use SLAB_DESTROY_BY_RCU

On Fri, Mar 25, 2016 at 03:29:24PM -0700, Eric Dumazet wrote:
> Tom Herbert would like to avoid touching UDP socket refcnt for encapsulated
> traffic. For this to happen, we need to use normal RCU rules, with a grace
> period before freeing a socket. UDP sockets are not short lived in the
> high usage case, so the added cost of call_rcu() should not be a concern.
> 
> This actually removes a lot of complexity in UDP stack
> 
> Multicast receives no longer need to hold a bucket lock.
> 
> Note that ip early demux still needs to take a reference on the socket.
> 
> Same remark for functions used by xt_socket and xt_PROXY netfilter modules,
> but this might be changed later.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Tom Herbert <tom@...bertland.com>
> ---
>  include/linux/udp.h |   8 +-
>  include/net/sock.h  |  12 +--
>  include/net/udp.h   |   2 +-
>  net/ipv4/udp.c      | 290 +++++++++++++++-------------------------------------
>  net/ipv4/udp_diag.c |  18 ++--
>  net/ipv6/udp.c      | 194 +++++++++++------------------------
>  6 files changed, 162 insertions(+), 362 deletions(-)

great stuff!