linux-kernel - Re: [PATCH net-next v6 8/10] xen-netback: Add stat counters for frag

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Message-ID: <20140305123546.GI19620@zion.uk.xensource.com>
Date:	Wed, 5 Mar 2014 12:35:47 +0000
From:	Wei Liu <wei.liu2@...rix.com>
To:	Zoltan Kiss <zoltan.kiss@...rix.com>
CC:	<ian.campbell@...rix.com>, <wei.liu2@...rix.com>,
	<xen-devel@...ts.xenproject.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <jonathan.davies@...rix.com>
Subject: Re: [PATCH net-next v6 8/10] xen-netback: Add stat counters for
 frag_list skbs

On Tue, Mar 04, 2014 at 10:32:19PM +0000, Zoltan Kiss wrote:
> These counters help determine how often the guest sends a packet with more
> than MAX_SKB_FRAGS frags.
> 
> NOTE: if bisect brought you here, you should apply the series up until #9,
> otherwise malicious guests can block other guests by not releasing their sent
> packets.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss@...rix.com>
> ---
>  drivers/net/xen-netback/common.h    |    1 +
>  drivers/net/xen-netback/interface.c |    7 +++++++
>  drivers/net/xen-netback/netback.c   |    1 +
>  3 files changed, 9 insertions(+)
> 
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> index eac171e..d8a2298 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -170,6 +170,7 @@ struct xenvif {
>  	unsigned long tx_zerocopy_sent;
>  	unsigned long tx_zerocopy_success;
>  	unsigned long tx_zerocopy_fail;
> +	unsigned long tx_frag_overflow;
>  
>  	/* Miscellaneous private stuff. */
>  	struct net_device *dev;
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index adfed30..ba5be2f 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -252,6 +252,13 @@ static const struct xenvif_stat {
>  		"tx_zerocopy_fail",
>  		offsetof(struct xenvif, tx_zerocopy_fail)
>  	},
> +	/* Number of packets exceeding MAX_SKB_FRAG slots. You should use
> +	 * a guest with the same MAX_SKB_FRAG
> +	 */
> +	{
> +		"tx_frag_overflow",
> +		offsetof(struct xenvif, tx_frag_overflow)
> +	},

This patch break bisection with a cause different than "unable to handle
too many frags", because previous patch makes use of this
tx_frag_overflow. It's harmless to merge this one into previous one.

>  };
>  
>  static int xenvif_get_sset_count(struct net_device *dev, int
>  string_set)
--
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