Re: [dpdk-dev] [PATCH v6 1/2] examples/vhost: add ioat ring space count and check

["Hu, Jiayu" <jiayu.hu@intel.com>]

Hi Cheng,

> -----Original Message-----
> From: Jiang, Cheng1 <cheng1.jiang@intel.com>
> Sent: Monday, January 4, 2021 12:58 PM
> To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Yang, YvonneX
> <yvonnex.yang@intel.com>; Wang, Yinan <yinan.wang@intel.com>; Jiang,
> Cheng1 <cheng1.jiang@intel.com>
> Subject: [PATCH v6 1/2] examples/vhost: add ioat ring space count and check
> 
> Add ioat ring space count and check, if ioat ring space is not enough
> for the next async vhost packet enqueue, then just return to prevent
> enqueue failure. Add rte_ioat_completed_ops() fail handler.
> 
> Signed-off-by: Cheng Jiang <Cheng1.jiang@intel.com>
> ---
>  examples/vhost/ioat.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/examples/vhost/ioat.c b/examples/vhost/ioat.c
> index 71d8a1f1f5..679d1e2f58 100644
> --- a/examples/vhost/ioat.c
> +++ b/examples/vhost/ioat.c
> @@ -17,6 +17,7 @@ struct packet_tracker {
>  	unsigned short next_read;
>  	unsigned short next_write;
>  	unsigned short last_remain;
> +	unsigned short ioat_space;
>  };
> 
>  struct packet_tracker cb_tracker[MAX_VHOST_DEVICE];
> @@ -113,7 +114,7 @@ open_ioat(const char *value)
>  			goto out;
>  		}
>  		rte_rawdev_start(dev_id);
> -
> +		cb_tracker[dev_id].ioat_space = IOAT_RING_SIZE;
>  		dma_info->nr++;
>  		i++;
>  	}
> @@ -140,13 +141,9 @@ ioat_transfer_data_cb(int vid, uint16_t queue_id,
>  			src = descs[i_desc].src;
>  			dst = descs[i_desc].dst;
>  			i_seg = 0;
> +			if (cb_tracker[dev_id].ioat_space < src->nr_segs)
> +				break;
>  			while (i_seg < src->nr_segs) {
> -				/*
> -				 * TODO: Assuming that the ring space of the
> -				 * IOAT device is large enough, so there is no
> -				 * error here, and the actual error handling
> -				 * will be added later.
> -				 */
>  				rte_ioat_enqueue_copy(dev_id,
>  					(uintptr_t)(src->iov[i_seg].iov_base)
>  						+ src->offset,
> @@ -158,7 +155,8 @@ ioat_transfer_data_cb(int vid, uint16_t queue_id,
>  				i_seg++;
>  			}
>  			write &= mask;
> -			cb_tracker[dev_id].size_track[write] = i_seg;
> +			cb_tracker[dev_id].size_track[write] = src->nr_segs;
> +			cb_tracker[dev_id].ioat_space -= src->nr_segs;
>  			write++;
>  		}
>  	} else {
> @@ -178,17 +176,21 @@ ioat_check_completed_copies_cb(int vid, uint16_t
> queue_id,
>  {
>  	if (!opaque_data) {
>  		uintptr_t dump[255];
> -		unsigned short n_seg;
> +		int n_seg;
>  		unsigned short read, write;
>  		unsigned short nb_packet = 0;
>  		unsigned short mask = MAX_ENQUEUED_SIZE - 1;
>  		unsigned short i;
> +
>  		int dev_id = dma_bind[vid].dmas[queue_id * 2
>  				+ VIRTIO_RXQ].dev_id;
>  		n_seg = rte_ioat_completed_ops(dev_id, 255, dump, dump);
> -		n_seg += cb_tracker[dev_id].last_remain;
>  		if (!n_seg)
>  			return 0;
> +
> +		cb_tracker[dev_id].ioat_space += n_seg;
> +		n_seg += cb_tracker[dev_id].last_remain;

When error happens in rte_ioat_completed_ops(), where n_seg is -1,
the value of "!n_seg" is false (0) and it can still pass the check of "if".

Thanks,
Jiayu
> +
>  		read = cb_tracker[dev_id].next_read;
>  		write = cb_tracker[dev_id].next_write;
>  		for (i = 0; i < max_packets; i++) {
> --
> 2.29.2