Re: [dpdk-dev] [PATCH] vhost: add unsafe API to check inflight packets

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi Xuan,

> -----Original Message-----
> From: Ding, Xuan <xuan.ding@intel.com>
> Sent: Thursday, September 9, 2021 1:58 PM
> To: dev@dpdk.org; maxime.coquelin@redhat.com; Xia, Chenbo
> <chenbo.xia@intel.com>
> Cc: Hu, Jiayu <jiayu.hu@intel.com>; cheng.jiang@intel.com; Richardson, Bruce
> <bruce.richardson@intel.com>; Pai G, Sunil <sunil.pai.g@intel.com>; Ding, Xuan
> <xuan.ding@intel.com>
> Subject: [PATCH] vhost: add unsafe API to check inflight packets
> 
> In async data path, when vring state changes, it is necessary to
> know the number of inflight packets in DMA engine. This patch
> provides a thread unsafe API to return the number of inflight
> packets without using any lock.
> 
> Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> ---
>  doc/guides/prog_guide/vhost_lib.rst    |  5 +++++
>  doc/guides/rel_notes/release_21_11.rst |  5 +++++
>  lib/vhost/rte_vhost_async.h            | 14 ++++++++++++++
>  lib/vhost/version.map                  |  3 +++
>  lib/vhost/vhost.c                      | 25 +++++++++++++++++++++++++
>  5 files changed, 52 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/vhost_lib.rst
> b/doc/guides/prog_guide/vhost_lib.rst
> index 8874033165..b4b1134f54 100644
> --- a/doc/guides/prog_guide/vhost_lib.rst
> +++ b/doc/guides/prog_guide/vhost_lib.rst
> @@ -305,6 +305,11 @@ The following is an overview of some key Vhost API
> functions:
>    This function returns the amount of in-flight packets for the vhost
>    queue using async acceleration.
> 
> +    ``rte_vhost_async_get_inflight_thread_unsafe(vid, queue_id)``
> +
> +  Get the number of inflight packets for a vhost queue without
> +  performing any locking.
> +
>  * ``rte_vhost_clear_queue_thread_unsafe(vid, queue_id, **pkts, count)``

This does not align with others. Please check.

> 
>    Clear inflight packets which are submitted to DMA engine in vhost async
> data
> diff --git a/doc/guides/rel_notes/release_21_11.rst
> b/doc/guides/rel_notes/release_21_11.rst
> index 675b573834..db080e9490 100644
> --- a/doc/guides/rel_notes/release_21_11.rst
> +++ b/doc/guides/rel_notes/release_21_11.rst
> @@ -55,6 +55,11 @@ New Features
>       Also, make sure to start the actual text at the margin.
>       =======================================================
> 
> +* **Added vhost API to get the number of inflight packets.**
> +
> +  Added an API which can get the number of inflight packets in
> +  vhost async data path.
> +

Please add 'without lock' or something similar as we already have a lock version.

>  * **Enabled new devargs parser.**
> 
>    * Enabled devargs syntax
> diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
> index b25ff446f7..0af414bf78 100644
> --- a/lib/vhost/rte_vhost_async.h
> +++ b/lib/vhost/rte_vhost_async.h
> @@ -246,6 +246,20 @@ uint16_t rte_vhost_poll_enqueue_completed(int vid,
> uint16_t queue_id,
>  __rte_experimental
>  int rte_vhost_async_get_inflight(int vid, uint16_t queue_id);
> 
> +/**
> + * This function is lock-free version to return the amount of in-flight
> + * packets for the vhost queue which uses async channel acceleration.
> + *
> + * @param vid
> + *  id of vhost device to enqueue data
> + * @param queue_id
> + *  queue id to enqueue data

You can also check dequeue inflight packets, right?

> + * @return
> + *  the amount of in-flight packets on success; -1 on failure
> + */
> +__rte_experimental
> +int rte_vhost_async_get_inflight_thread_unsafe(int vid, uint16_t queue_id);
> +
>  /**
>   * This function checks async completion status and clear packets for
>   * a specific vhost device queue. Packets which are inflight will be
> diff --git a/lib/vhost/version.map b/lib/vhost/version.map
> index c92a9d4962..b150dc408d 100644
> --- a/lib/vhost/version.map
> +++ b/lib/vhost/version.map
> @@ -85,4 +85,7 @@ EXPERIMENTAL {
>  	rte_vhost_async_channel_register_thread_unsafe;
>  	rte_vhost_async_channel_unregister_thread_unsafe;
>  	rte_vhost_clear_queue_thread_unsafe;
> +
> +	#added in 21.11
> +	rte_vhost_async_get_inflight_thread_unsafe;
>  };
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index 355ff37651..df96f84873 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -1886,5 +1886,30 @@ int rte_vhost_async_get_inflight(int vid, uint16_t
> queue_id)
>  	return ret;
>  }
> 
> +int rte_vhost_async_get_inflight_thread_unsafe(int vid, uint16_t queue_id)

According to DPDK coding style, return type and func name should be in different
lines. I notice there are also some left to clean. May clean in another patch.

Thanks,
Chenbo 

> +{
> +	struct vhost_virtqueue *vq;
> +	struct virtio_net *dev = get_device(vid);
> +	int ret = -1;
> +
> +	if (dev == NULL)
> +		return ret;
> +
> +	if (queue_id >= VHOST_MAX_VRING)
> +		return ret;
> +
> +	vq = dev->virtqueue[queue_id];
> +
> +	if (vq == NULL)
> +		return ret;
> +
> +	if (!vq->async_registered)
> +		return ret;
> +
> +	ret = vq->async_pkts_inflight_n;
> +
> +	return ret;
> +}
> +
>  RTE_LOG_REGISTER_SUFFIX(vhost_config_log_level, config, INFO);
>  RTE_LOG_REGISTER_SUFFIX(vhost_data_log_level, data, WARNING);
> --
> 2.17.1