Re: [Xen-devel] [PATCH net-next V7 3/4] xen-netback: coalesce slots in TX path and fix regressions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.04.13 at 14:20, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> --- a/include/xen/interface/io/netif.h
> +++ b/include/xen/interface/io/netif.h
> @@ -13,6 +13,24 @@
>  #include <xen/interface/grant_table.h>
>  
>  /*
> + * Older implementation of Xen network frontend / backend has an
> + * implicit dependency on the MAX_SKB_FRAGS as the maximum number of
> + * ring slots a skb can use. Netfront / netback may not work as
> + * expected when frontend and backend have different MAX_SKB_FRAGS.
> + *
> + * A better approach is to add mechanism for netfront / netback to
> + * negotiate this value. However we cannot fix all possible
> + * frontends, so we need to define a value which states the minimum
> + * slots backend must support.
> + *
> + * The minimum value derives from older Linux kernel's MAX_SKB_FRAGS
> + * (18), which is proved to work with most frontends. Any new backend
> + * which doesn't negotiate with frontend should expect frontend to
> + * send a valid packet using slots up to this value.
> + */
> +#define XEN_NETIF_NR_SLOTS_MIN 18
> +
> +/*
>   * Notifications after enqueuing any type of message should be conditional on
>   * the appropriate req_event or rsp_event field in the shared ring.
>   * If the client sends notification for rx requests then it should specify

Just like with the other public header change in this series - care
to submit a patch against xen-unstable, to have the master copy
of the header updated?

Jan


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