Magnus Karlsson wrote:
> From: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
>
> Introduce one cache line worth of padding between the consumer pointer
> and the flags field as well as between the flags field and the start
> of the descriptors in all the lockless rings. This so that the x86 HW
> adjacency prefetcher will not prefetch the adjacent pointer/field when
> only one pointer/field is going to be used. This improves throughput
> performance for the l2fwd sample app with 1% on my machine with HW
> prefetching turned on in the BIOS.
>
> Signed-off-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> ---
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
> net/xdp/xsk_queue.h | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> index cdb9cf3..74fac80 100644
> --- a/net/xdp/xsk_queue.h
> +++ b/net/xdp/xsk_queue.h
> @@ -18,9 +18,11 @@ struct xdp_ring {
> /* Hinder the adjacent cache prefetcher to prefetch the consumer
> * pointer if the producer pointer is touched and vice versa.
> */
> - u32 pad ____cacheline_aligned_in_smp;
> + u32 pad1 ____cacheline_aligned_in_smp;
> u32 consumer ____cacheline_aligned_in_smp;
> + u32 pad2 ____cacheline_aligned_in_smp;
> u32 flags;
> + u32 pad3 ____cacheline_aligned_in_smp;
> };
>
> /* Used for the RX and TX queues for packets */
> --
> 2.7.4
>
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