netdev - Re: [net-next PATCH V3 1/3] net: adjust napi_consume

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Message-ID: <56E1AD33.3020507@cogentembedded.com>
Date:	Thu, 10 Mar 2016 20:21:55 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Cc:	eugenia@...lanox.com, Alexander Duyck <alexander.duyck@...il.com>,
	alexei.starovoitov@...il.com, saeedm@...lanox.com,
	gerlitz.or@...il.com
Subject: Re: [net-next PATCH V3 1/3] net: adjust napi_consume_skb to handle
 none-NAPI callers

Hello.

On 03/10/2016 05:59 PM, Jesper Dangaard Brouer wrote:

> Some drivers reuse/share code paths that free SKBs between NAPI
> and none-NAPI calls. Adjust napi_consume_skb to handle this
> use-case.
>
> Before, calls from netpoll (w/ IRQs disabled) was handled and
> indicated with a budget zero indication.  Use the same zero
> indication to handle calls not originating from NAPI/softirq.
> Simply handled by using dev_consume_skb_any().
>
> This adds an extra branch+call for the netpoll case (checking
> in_irq() + irqs_disabled()), but that is okay as this is a slowpath.
>
> Suggested-by: Alexander Duyck <aduyck@...antis.com>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> ---
>   net/core/skbuff.c |    4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 7af7ec635d90..bc62baa54ceb 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -801,9 +801,9 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
>   	if (unlikely(!skb))
>   		return;
>
> -	/* if budget is 0 assume netpoll w/ IRQs disabled */
> +	/* Zero budget indicate none-NAPI context called us, like netpoll */

    Non-NAPI?

[...]

MBR, Sergei