netdev - Re: [PATCH net-next 2/2] net:add socket option for low latency polling

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Message-ID: <1370961930.3252.32.camel@edumazet-glaptop>
Date:	Tue, 11 Jun 2013 07:45:30 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
Cc:	David 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>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
	Eilon Greenstien <eilong@...adcom.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Amir Vadai <amirv@...lanox.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH net-next 2/2] net:add socket option for low latency
 polling

On Tue, 2013-06-11 at 17:24 +0300, Eliezer Tamir wrote:
> adds a socket option for low latency polling.
> This allows overriding the global sysctl value with a per-socket one.
> 
> Signed-off-by: Eliezer Tamir <eliezer.tamir@...ux.intel.com>
> ---
> 
>  
> -static inline cycles_t ll_end_time(void)
> +static inline cycles_t ll_end_time(struct sock *sk)
>  {
> -	return TSC_MHZ * ACCESS_ONCE(sysctl_net_ll_poll) + get_cycles();
> +	return TSC_MHZ * ACCESS_ONCE(sk->sk_ll_usec) + get_cycles();
>  }

Hmm, sk_ll_usec is an unsigned int.

(cycles_t)TSC_MHZ * ACCESS_ONCE(sk->sk_ll_usec) + get_cycles();

>  
> +#ifdef CONFIG_NET_LL_RX_POLL
> +	case SO_LL:
> +		if (!capable(CAP_NET_ADMIN))
> +			ret = -EACCES;
> +		else {
> +			unsigned long ulval;

Why an "unsigned long" ?


> +
> +			if (!copy_from_user(&ulval, optval, sizeof(ulval))
> +							&& ulval >= 0)
> +				sk->sk_ll_usec = ulval;
> +
> +			else
> +				ret = -EINVAL;

Just use
	sk->sk_ll_usec = val;

> +
> +		}
> +		break;
> +#endif
>  	default:
>  		ret = -ENOPROTOOPT;
>  		break;
> @@ -944,6 +961,7 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
>  
>  	union {
>  		int val;
> +		unsigned long ulval;

Why an unsigned long ? 32bit are more than enough.

>  		struct linger ling;
>  		struct timeval tm;
>  	} v;
> @@ -1170,6 +1188,13 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
>  		v.val = sock_flag(sk, SOCK_SELECT_ERR_QUEUE);
>  		break;
>  
> +#ifdef CONFIG_NET_LL_RX_POLL
> +	case SO_LL:
> +		len = sizeof(v.ulval);
> +		v.ulval = sk->sk_ll_usec;
> +		break;
> +#endif
> +



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