From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Xing, Beilei" <beilei.xing@intel.com>,
"Zhang, Qi Z" <qi.z.zhang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, "stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2] net/i40e: fix Rx instability with vector mode
Date: Fri, 26 Oct 2018 08:47:02 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB9772580102FED12C@IRSMSX106.ger.corp.intel.com> (raw)
In-Reply-To: <1540535607-115720-1-git-send-email-beilei.xing@intel.com>
Hi,
>
> Previously, there is instability during vector Rx if descriptor
> number is not power of 2, e.g. process hang and some Rx packets
> are unexpectedly empty. That's because vector Rx mode assumes Rx
> descriptor number is power of 2 when doing bit mask.
> This patch allows vector mode only when the number of Rx descriptor
> is power of 2.
>
> Fixes: 8e109464c022 ("i40e: allow vector Rx and Tx usage")
> Fixes: a3c83a2527e1 ("net/i40e: enable runtime queue setup")
> Cc: stable@dpdk.org
>
> Signed-off-by: Beilei Xing <beilei.xing@intel.com>
> ---
>
> v2 changes:
> - rx_vec_allowed is global configuration, avoid overwrite.
>
> doc/guides/nics/i40e.rst | 7 +++++++
> drivers/net/i40e/i40e_rxtx.c | 13 ++++++++++++-
> 2 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst
> index ab3928a..bfacbd1 100644
> --- a/doc/guides/nics/i40e.rst
> +++ b/doc/guides/nics/i40e.rst
> @@ -172,6 +172,13 @@ Runtime Config Options
>
> -w 84:00.0,use-latest-supported-vec=1
>
> +Vector RX Pre-conditions
> +~~~~~~~~~~~~~~~~~~~~~~~~
> +For Vector RX it is assumed that the number of descriptor rings will be a power
> +of 2. With this pre-condition, the ring pointer can easily scroll back to the
> +head after hitting the tail without a conditional check. In addition Vector RX
> +can use this assumption to do a bit mask using ``ring_size - 1``.
> +
> Driver compilation and testing
> ------------------------------
>
> diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
> index a827456..f6dcca0 100644
> --- a/drivers/net/i40e/i40e_rxtx.c
> +++ b/drivers/net/i40e/i40e_rxtx.c
> @@ -1735,10 +1735,14 @@ i40e_dev_rx_queue_setup_runtime(struct rte_eth_dev *dev,
> * i40e_set_rx_function.
> */
> ad->rx_bulk_alloc_allowed = true;
> - ad->rx_vec_allowed = true;
> dev->data->scattered_rx = use_scattered_rx;
> if (use_def_burst_func)
> ad->rx_bulk_alloc_allowed = false;
> + /**
> + * Vector mode is allowed only when number of Rx queue
> + * descriptor is a power of 2.
> + */
> + ad->rx_vec_allowed = !(rxq->nb_rx_desc & (rxq->nb_rx_desc - 1));
> i40e_set_rx_function(dev);
> return 0;
> }
I think this is not complete - if it is not the first function, we have to do:
If (if (ad->rx_vec_allowed && (rxq->nb_rx_desc & (rxq->nb_rx_desc - 1) != 0) {
PMD_DRV_LOG(ERR, ...);
return -EINVAL;
}
BTW, here and below why not to use rte_is_power_of_2()?
Konstantin
> @@ -1811,6 +1815,13 @@ i40e_dev_rx_queue_setup(struct rte_eth_dev *dev,
> return -EINVAL;
> }
>
> + /**
> + * Vector mode is allowed only when number of Rx queue
> + * descriptor is a power of 2.
> + */
> + if (ad->rx_vec_allowed)
> + ad->rx_vec_allowed = !(nb_desc & (nb_desc - 1));
> +
> /* Free memory if needed */
> if (dev->data->rx_queues[queue_idx]) {
> i40e_dev_rx_queue_release(dev->data->rx_queues[queue_idx]);
next prev parent reply other threads:[~2018-10-26 8:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-25 7:40 [dpdk-dev] [PATCH] " Beilei Xing
2018-10-25 16:47 ` Zhang, Qi Z
2018-10-26 6:33 ` [dpdk-dev] [PATCH v2] " Beilei Xing
2018-10-26 8:47 ` Ananyev, Konstantin [this message]
2018-10-26 15:41 ` Zhang, Qi Z
2018-10-29 1:48 ` Xing, Beilei
2018-10-26 11:11 ` Bruce Richardson
2018-10-26 15:49 ` Zhang, Qi Z
2018-11-01 5:53 ` [dpdk-dev] [PATCH v3] " Beilei Xing
2018-11-01 11:48 ` Ananyev, Konstantin
2018-11-01 13:13 ` Zhang, Qi Z
2018-11-05 3:18 ` [dpdk-dev] [PATCH v4] " Beilei Xing
2018-11-05 11:05 ` Ananyev, Konstantin
2018-11-05 15:53 ` Zhang, Qi Z
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