linux-kernel - Re: [PATCH v5 net-next 2/5] net: implement support for low latency socket polling

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Date:	Mon, 27 May 2013 17:26:21 -0700
From:	Eric Dumazet <eric.dumazet@...il.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>,
	Eilon Greenstien <eilong@...adcom.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Alex Rosenbaum <alexr@...lanox.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH v5 net-next 2/5] net: implement support for low latency
 socket polling

On Mon, 2013-05-27 at 10:44 +0300, Eliezer Tamir wrote:

> diff --git a/include/net/sock.h b/include/net/sock.h
> index 66772cf..c7c3ea6 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -281,6 +281,7 @@ struct cg_proto;
>    *	@sk_error_report: callback to indicate errors (e.g. %MSG_ERRQUEUE)
>    *	@sk_backlog_rcv: callback to process the backlog
>    *	@sk_destruct: called at sock freeing time, i.e. when all refcnt == 0
> +  *	@sk_napi_id: id of the last napi context to receive data for sk
>   */
>  struct sock {
>  	/*
> @@ -399,6 +400,9 @@ struct sock {
>  	int			(*sk_backlog_rcv)(struct sock *sk,
>  						  struct sk_buff *skb);
>  	void                    (*sk_destruct)(struct sock *sk);
> +#ifdef CONFIG_NET_LL_RX_POLL
> +	unsigned int		sk_napi_id;
> +#endif
>  };

I believe this is a bad choice for data locality.

I would rather move it in the same cache line than sk_rxhash



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