Re: [dpdk-dev] [PATCH v3 2/2] ring: use wfe to wait for ring tail update on aarch64

[Jerin Jacob <jerinjacobk@gmail.com>]

On Sun, Apr 25, 2021 at 11:27 AM Ruifeng Wang <ruifeng.wang@arm.com> wrote:
>
> Instead of polling for tail to be updated, use wfe instruction.
>
> Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Reviewed-by: Steve Capper <steve.capper@arm.com>
> Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

Acked-by: Jerin Jacob <jerinj@marvell.com>



> ---
>  lib/ring/rte_ring_c11_pvt.h     | 4 ++--
>  lib/ring/rte_ring_generic_pvt.h | 3 +--
>  2 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/lib/ring/rte_ring_c11_pvt.h b/lib/ring/rte_ring_c11_pvt.h
> index 759192f4c4..37e0b2afd6 100644
> --- a/lib/ring/rte_ring_c11_pvt.h
> +++ b/lib/ring/rte_ring_c11_pvt.h
> @@ -2,6 +2,7 @@
>   *
>   * Copyright (c) 2017,2018 HXT-semitech Corporation.
>   * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org
> + * Copyright (c) 2021 Arm Limited
>   * All rights reserved.
>   * Derived from FreeBSD's bufring.h
>   * Used as BSD-3 Licensed with permission from Kip Macy.
> @@ -21,8 +22,7 @@ __rte_ring_update_tail(struct rte_ring_headtail *ht, uint32_t old_val,
>          * we need to wait for them to complete
>          */
>         if (!single)
> -               while (unlikely(ht->tail != old_val))
> -                       rte_pause();
> +               rte_wait_until_equal_32(&ht->tail, old_val, __ATOMIC_RELAXED);
>
>         __atomic_store_n(&ht->tail, new_val, __ATOMIC_RELEASE);
>  }
> diff --git a/lib/ring/rte_ring_generic_pvt.h b/lib/ring/rte_ring_generic_pvt.h
> index 532deb5e7a..c95ad7e12c 100644
> --- a/lib/ring/rte_ring_generic_pvt.h
> +++ b/lib/ring/rte_ring_generic_pvt.h
> @@ -23,8 +23,7 @@ __rte_ring_update_tail(struct rte_ring_headtail *ht, uint32_t old_val,
>          * we need to wait for them to complete
>          */
>         if (!single)
> -               while (unlikely(ht->tail != old_val))
> -                       rte_pause();
> +               rte_wait_until_equal_32(&ht->tail, old_val, __ATOMIC_RELAXED);
>
>         ht->tail = new_val;
>  }
> --
> 2.25.1
>