Re: [Xen-devel] [PATCH V4 net-next 1/5] xen-netback: Factor queue-specific data into queue struct.

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew J. Bennieston [mailto:andrew.bennieston@xxxxxxxxxx]
> Sent: 17 February 2014 17:58
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Ian Campbell; Wei Liu; Paul Durrant; netdev@xxxxxxxxxxxxxxx; David
> Vrabel; Andrew Bennieston
> Subject: [PATCH V4 net-next 1/5] xen-netback: Factor queue-specific data
> into queue struct.
> 
> From: "Andrew J. Bennieston" <andrew.bennieston@xxxxxxxxxx>
> 
> In preparation for multi-queue support in xen-netback, move the
> queue-specific data from struct xenvif into struct xenvif_queue, and
> update the rest of the code to use this.
> 
> Also adds loops over queues where appropriate, even though only one is
> configured at this point, and uses alloc_netdev_mq() and the
> corresponding multi-queue netif wake/start/stop functions in preparation
> for multiple active queues.
> 
> Finally, implements a trivial queue selection function suitable for
> ndo_select_queue, which simply returns 0 for a single queue and uses
> skb_get_hash() to compute the queue index otherwise.
> 
> Signed-off-by: Andrew J. Bennieston <andrew.bennieston@xxxxxxxxxx>
> ---
>  drivers/net/xen-netback/common.h    |   81 ++++--
>  drivers/net/xen-netback/interface.c |  314 ++++++++++++++-------
>  drivers/net/xen-netback/netback.c   |  528 ++++++++++++++++++------------
> -----
>  drivers/net/xen-netback/xenbus.c    |   87 ++++--
>  4 files changed, 593 insertions(+), 417 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-
> netback/common.h
> index ae413a2..2550867 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -108,17 +108,36 @@ struct xenvif_rx_meta {
>   */
>  #define MAX_GRANT_COPY_OPS (MAX_SKB_FRAGS *
> XEN_NETIF_RX_RING_SIZE)
> 
> -struct xenvif {
> -     /* Unique identifier for this interface. */
> -     domid_t          domid;
> -     unsigned int     handle;
> +/* Queue name is interface name with "-qNNN" appended */
> +#define QUEUE_NAME_SIZE (IFNAMSIZ + 6)
> +

'-qNNN' is only 5 chars. Are you accounting for a NUL terminator too?

> +/* IRQ name is queue name with "-tx" or "-rx" appended */
> +#define IRQ_NAME_SIZE (QUEUE_NAME_SIZE + 4)
> +

If yes, then you appear to have doubly accounted for it here.

> +struct xenvif;
> +
> +struct xenvif_stats {
> +     /* Stats fields to be updated per-queue.
> +      * A subset of struct net_device_stats that contains only the
> +      * fields that are updated in netback.c for each queue.
> +      */
> +     unsigned int rx_bytes;
> +     unsigned int rx_packets;
> +     unsigned int tx_bytes;
> +     unsigned int tx_packets;
> +};
> +
> +struct xenvif_queue { /* Per-queue data for xenvif */
> +     unsigned int id; /* Queue ID, 0-based */
> +     char name[QUEUE_NAME_SIZE]; /* DEVNAME-qN */
> +     struct xenvif *vif; /* Parent VIF */
> 
>       /* Use NAPI for guest TX */
>       struct napi_struct napi;
>       /* When feature-split-event-channels = 0, tx_irq = rx_irq. */
>       unsigned int tx_irq;
>       /* Only used when feature-split-event-channels = 1 */
> -     char tx_irq_name[IFNAMSIZ+4]; /* DEVNAME-tx */
> +     char tx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-tx */
>       struct xen_netif_tx_back_ring tx;
>       struct sk_buff_head tx_queue;
>       struct page *mmap_pages[MAX_PENDING_REQS];
> @@ -140,19 +159,34 @@ struct xenvif {
>       /* When feature-split-event-channels = 0, tx_irq = rx_irq. */
>       unsigned int rx_irq;
>       /* Only used when feature-split-event-channels = 1 */
> -     char rx_irq_name[IFNAMSIZ+4]; /* DEVNAME-rx */
> +     char rx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-rx */
>       struct xen_netif_rx_back_ring rx;
>       struct sk_buff_head rx_queue;
>       RING_IDX rx_last_skb_slots;
> 
> -     /* This array is allocated seperately as it is large */
> -     struct gnttab_copy *grant_copy_op;
> +     struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];
> 
>       /* We create one meta structure per ring request we consume, so
>        * the maximum number is the same as the ring size.
>        */
>       struct xenvif_rx_meta meta[XEN_NETIF_RX_RING_SIZE];
> 
> +     /* Transmit shaping: allow 'credit_bytes' every 'credit_usec'. */
> +     unsigned long   credit_bytes;
> +     unsigned long   credit_usec;
> +     unsigned long   remaining_credit;
> +     struct timer_list credit_timeout;
> +     u64 credit_window_start;
> +
> +     /* Statistics */
> +     struct xenvif_stats stats;
> +};
> +
> +struct xenvif {
> +     /* Unique identifier for this interface. */
> +     domid_t          domid;
> +     unsigned int     handle;
> +
>       u8               fe_dev_addr[6];
> 
>       /* Frontend feature information. */
> @@ -166,15 +200,12 @@ struct xenvif {
>       /* Internal feature information. */
>       u8 can_queue:1;     /* can queue packets for receiver? */
> 
> -     /* Transmit shaping: allow 'credit_bytes' every 'credit_usec'. */
> -     unsigned long   credit_bytes;
> -     unsigned long   credit_usec;
> -     unsigned long   remaining_credit;
> -     struct timer_list credit_timeout;
> -     u64 credit_window_start;
> +     /* Queues */
> +     unsigned int num_queues;
> +     struct xenvif_queue *queues;
> 
>       /* Statistics */
> -     unsigned long rx_gso_checksum_fixup;
> +     atomic_t rx_gso_checksum_fixup;

Any reason why this is not in xenvif_stats? If  it were there then it would not 
need to be atomic.

  Paul

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