Subject: Re: [Xen-devel] [PATCH v2 net-next 5/7] xen-netback: process guest rx packets in batches

From: Konrad Rzeszutek Wilk <[email-masked]>
Date: Tue, 4 Oct 2016 08:47:44 -0400

On Tue, Oct 04, 2016 at 10:29:16AM +0100, Paul Durrant wrote:
> From: David Vrabel <[email-masked]>
> 
> Instead of only placing one skb on the guest rx ring at a time, process
> a batch of up-to 64.  This improves performance by ~10% in some tests.

And does it regress latency workloads?

What are those 'some tests' you speak off?

Thanks.
> 
> Signed-off-by: David Vrabel <[email-masked]>
> [re-based]
> Signed-off-by: Paul Durrant <[email-masked]>
> ---
> Cc: Wei Liu <[email-masked]>
> ---
>  drivers/net/xen-netback/rx.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
> index 9548709..ae822b8 100644
> --- a/drivers/net/xen-netback/rx.c
> +++ b/drivers/net/xen-netback/rx.c
> @@ -399,7 +399,7 @@ static void xenvif_rx_extra_slot(struct xenvif_queue *queue,
>  	BUG();
>  }
>  
> -void xenvif_rx_action(struct xenvif_queue *queue)
> +void xenvif_rx_skb(struct xenvif_queue *queue)
>  {
>  	struct xenvif_pkt_state pkt;
>  
> @@ -425,6 +425,19 @@ void xenvif_rx_action(struct xenvif_queue *queue)
>  	xenvif_rx_complete(queue, &pkt);
>  }
>  
> +#define RX_BATCH_SIZE 64
> +
> +void xenvif_rx_action(struct xenvif_queue *queue)
> +{
> +	unsigned int work_done = 0;
> +
> +	while (xenvif_rx_ring_slots_available(queue) &&
> +	       work_done < RX_BATCH_SIZE) {
> +		xenvif_rx_skb(queue);
> +		work_done++;
> +	}
> +}
> +
>  static bool xenvif_rx_queue_stalled(struct xenvif_queue *queue)
>  {
>  	RING_IDX prod, cons;
> -- 
> 2.1.4
> 
> 
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