Re: [dpdk-dev] [PATCH v5 4/4] examples/vhost: support vhost async dequeue data path

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 7/5/21 8:11 PM, Wenwu Ma wrote:
> This patch is to add vhost async dequeue data-path in vhost sample.
> vswitch can leverage IOAT to accelerate vhost async dequeue data-path.

"
This patch adds support for async dequeue path to Vhost example.
"

> Signed-off-by: Wenwu Ma <wenwux.ma@intel.com>
> ---
>  doc/guides/sample_app_ug/vhost.rst |   9 +-
>  examples/vhost/ioat.c              |  61 ++++++++++---
>  examples/vhost/ioat.h              |  25 ++++++
>  examples/vhost/main.c              | 140 ++++++++++++++++++++---------
>  4 files changed, 177 insertions(+), 58 deletions(-)
> 
> diff --git a/doc/guides/sample_app_ug/vhost.rst b/doc/guides/sample_app_ug/vhost.rst
> index 9afde9c7f5..63dcf181e1 100644
> --- a/doc/guides/sample_app_ug/vhost.rst
> +++ b/doc/guides/sample_app_ug/vhost.rst
> @@ -169,9 +169,12 @@ demonstrates how to use the async vhost APIs. It's used in combination with dmas
>  **--dmas**
>  This parameter is used to specify the assigned DMA device of a vhost device.
>  Async vhost-user net driver will be used if --dmas is set. For example
> ---dmas [txd0@00:04.0,txd1@00:04.1] means use DMA channel 00:04.0 for vhost
> -device 0 enqueue operation and use DMA channel 00:04.1 for vhost device 1
> -enqueue operation.
> +--dmas [txd0@00:04.0,txd1@00:04.1,rxd0@00:04.2,rxd1@00:04.3] means use
> +DMA channel 00:04.0/00:04.2 for vhost device 0 enqueue/dequeue operation
> +and use DMA channel 00:04.1/00:04.3 for vhost device 1 enqueue/dequeue
> +operation. The index of the device corresponds to the socket file in order,
> +that means vhost device 0 is created through the first socket file, vhost
> +device 1 is created through the second socket file, and so on.
>  
>  Common Issues
>  -------------
> diff --git a/examples/vhost/ioat.c b/examples/vhost/ioat.c
> index bf4e033bdb..a305100b47 100644
> --- a/examples/vhost/ioat.c
> +++ b/examples/vhost/ioat.c
> @@ -21,6 +21,8 @@ struct packet_tracker {
>  
>  struct packet_tracker cb_tracker[MAX_VHOST_DEVICE];
>  
> +int vid2socketid[MAX_VHOST_DEVICE];
> +
>  int
>  open_ioat(const char *value)
>  {
> @@ -29,7 +31,7 @@ open_ioat(const char *value)
>  	char *addrs = input;
>  	char *ptrs[2];
>  	char *start, *end, *substr;
> -	int64_t vid, vring_id;
> +	int64_t socketid, vring_id;
>  	struct rte_ioat_rawdev_config config;
>  	struct rte_rawdev_info info = { .dev_private = &config };
>  	char name[32];
> @@ -60,6 +62,8 @@ open_ioat(const char *value)
>  		goto out;
>  	}
>  	while (i < args_nr) {
> +		char *txd, *rxd;
> +		bool is_txd;
>  		char *arg_temp = dma_arg[i];
>  		uint8_t sub_nr;
>  		sub_nr = rte_strsplit(arg_temp, strlen(arg_temp), ptrs, 2, '@');
> @@ -68,27 +72,38 @@ open_ioat(const char *value)
>  			goto out;
>  		}
>  
> -		start = strstr(ptrs[0], "txd");
> -		if (start == NULL) {
> +		int async_flag;
> +		txd = strstr(ptrs[0], "txd");
> +		rxd = strstr(ptrs[0], "rxd");
> +		if (txd == NULL && rxd == NULL) {
>  			ret = -1;
>  			goto out;
> +		} else if (txd) {
> +			is_txd = true;
> +			start = txd;
> +			async_flag = ASYNC_RX_VHOST;

That's confusing to set ASYNC_RX_VHOST flag when txd is present.
IIUC, this is about the enqueue path, so TX from Vhost point of view.
So either name the flag ASYNC_TX_VHOST or ASYNV_ENQUEUE_VHOST?

> +		} else {
> +			is_txd = false;
> +			start = rxd;
> +			async_flag = ASYNC_TX_VHOST;
>  		}

What if both are set by the user? you might want to add a check.