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From: Stephen Hemminger <stephen@networkplumber.org>
To: Joyce Kong <joyce.kong@arm.com>
Cc: maxime.coquelin@redhat.com, tiwei.bie@intel.com,
	zhihong.wang@intel.com, thomas@monjalon.net, jerinj@marvell.com,
	yinan.wang@intel.com, honnappa.nagarahalli@arm.com,
	gavin.hu@arm.com, nd@arm.com, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2 1/2] virtio: one way barrier for split vring used idx
Date: Thu, 2 Apr 2020 08:47:56 -0700	[thread overview]
Message-ID: <20200402084756.2dc243ae@hermes.lan> (raw)
In-Reply-To: <20200402025753.31420-2-joyce.kong@arm.com>

On Thu,  2 Apr 2020 10:57:52 +0800
Joyce Kong <joyce.kong@arm.com> wrote:

> -					(vq)->vq_used_cons_idx))
> +static inline uint16_t
> +virtqueue_nused(struct virtqueue *vq)
vq is unmodified and should be const

> +{
> +	uint16_t idx;
> +	if (vq->hw->weak_barriers) {
Put blank line between declaration and if statement

> +/* x86 prefers to using rte_smp_rmb over __atomic_load_n as it reports
> + * a slightly better perf, which comes from the saved branch by the compiler.
> + * The if and else branches are identical with the smp and cio barriers both
> + * defined as compiler barriers on x86.
> + */

Do not put comments on left margin (except in function prolog).

> +#ifdef RTE_ARCH_X86_64
> +		idx = vq->vq_split.ring.used->idx;
> +		rte_smp_rmb();
> +#else
> +		idx = __atomic_load_n(&(vq)->vq_split.ring.used->idx,
> +				__ATOMIC_ACQUIRE);
> +#endif
> +	} else {
> +		idx = vq->vq_split.ring.used->idx;
> +		rte_cio_rmb();
> +	}
> +	return (idx - vq->vq_used_cons_idx);

Parenthesis around arguments to return are unnecessary.
BSD code likes it, Linux style does not.

> +}

This kind of arch specific code is hard to maintain.
Does it really make that much difference.

  reply	other threads:[~2020-04-02 15:48 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12  9:24 [dpdk-dev] [PATCH v1 0/2] one way barrier for split vring idx Joyce Kong
2020-02-12  9:24 ` [dpdk-dev] [PATCH v1 1/2] virtio: one way barrier for split vring used idx Joyce Kong
2020-02-12  9:24 ` [dpdk-dev] [PATCH v1 2/2] virtio: one way barrier for split vring avail idx Joyce Kong
2020-04-02  2:57 ` [dpdk-dev] [PATCH v2 0/2] one way barrier for split vring idx Joyce Kong
2020-04-02  2:57 ` [dpdk-dev] [PATCH v2 1/2] virtio: one way barrier for split vring used idx Joyce Kong
2020-04-02 15:47   ` Stephen Hemminger [this message]
2020-04-03  8:55     ` Gavin Hu
2020-04-16  4:40       ` Honnappa Nagarahalli
2020-04-16  6:46         ` Joyce Kong
2020-04-02  2:57 ` [dpdk-dev] [PATCH v2 2/2] virtio: one way barrier for split vring avail idx Joyce Kong
2020-04-06 15:26 ` [dpdk-dev] [PATCH v3 0/2] one way barrier for split vring idx Joyce Kong
2020-04-16  9:08   ` Ye Xiaolong
2020-04-06 15:26 ` [dpdk-dev] [PATCH v3 1/2] virtio: one way barrier for split vring used idx Joyce Kong
2020-04-17  6:51   ` Ye Xiaolong
2020-04-17  8:14     ` Joyce Kong
2020-04-06 15:26 ` [dpdk-dev] [PATCH v3 2/2] virtio: one way barrier for split vring avail idx Joyce Kong
2020-04-24  3:39 ` [dpdk-dev] [PATCH v4 0/2] one way barrier for split vring idx Joyce Kong
2020-04-28 16:06   ` Maxime Coquelin
2020-04-29 17:45   ` Ferruh Yigit
2020-04-30  9:09     ` Maxime Coquelin
2020-04-30  9:16       ` Joyce Kong
2020-04-30  9:24         ` Maxime Coquelin
2020-04-24  3:39 ` [dpdk-dev] [PATCH v4 1/2] virtio: one way barrier for split vring used idx Joyce Kong
2020-04-27  9:03   ` Maxime Coquelin
2020-04-24  3:39 ` [dpdk-dev] [PATCH v4 2/2] virtio: one way barrier for split vring avail idx Joyce Kong
2020-04-27  9:03   ` Maxime Coquelin
2020-04-30  9:14 ` [dpdk-dev] [PATCH v5 0/2] one way barrier for split vring idx Joyce Kong
2020-04-30 20:54   ` Maxime Coquelin
2020-04-30  9:14 ` [dpdk-dev] [PATCH v5 1/2] virtio: one way barrier for split vring used idx Joyce Kong
2020-04-30 22:58   ` Ferruh Yigit
2020-05-04 10:04     ` Maxime Coquelin
2020-04-30  9:14 ` [dpdk-dev] [PATCH v5 2/2] virtio: one way barrier for split vring avail idx Joyce Kong

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