linux-kernel - Re: [PATCH v4 net-next 2/4] tcp: add TCP support for low latency receive poll.

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Message-ID: <1369157418.2615.30.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Tue, 21 May 2013 18:30:18 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
CC:	Dave Miller <davem@...emloft.net>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	<e1000-devel@...ts.sourceforge.net>,
	Willem de Bruijn <willemb@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Eilon Greenstien <eilong@...adcom.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH v4 net-next 2/4] tcp: add TCP support for low latency
 receive poll.

On Tue, 2013-05-21 at 17:27 +0300, Eliezer Tamir wrote:
> adds busy-poll support for TCP.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
> Tested-by: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Eliezer Tamir <eliezer.tamir@...ux.intel.com>
> ---
> 
>  net/ipv4/tcp.c       |    9 +++++++++
>  net/ipv4/tcp_input.c |    4 ++++
>  2 files changed, 13 insertions(+), 0 deletions(-)
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index dcb116d..b9cc512 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
[...]
> @@ -1551,6 +1553,12 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
>  	struct sk_buff *skb;
>  	u32 urg_hole = 0;
>  
> +#ifdef CONFIG_INET_LL_RX_POLL
> +	if (sk_valid_ll(sk) && skb_queue_empty(&sk->sk_receive_queue)
> +	    && (sk->sk_state == TCP_ESTABLISHED))
> +		sk_poll_ll(sk, nonblock);
> +#endif
[...]

I don't think the #ifdef is needed; this should compile down to nothing
if the config option is disabled.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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