[dpdk-dev] [PATCH 2/2] net/netvsc: introduce driver parameter to control the use of external mbuf on receiving data

Ferruh Yigit ferruh.yigit at intel.com
Fri Oct 23 18:23:23 CEST 2020


On 10/22/2020 8:46 PM, Long Li wrote:
> From: Long Li <longli at microsoft.com>
> 
> When receiving packets, netvsp puts data in a buffer mapped through UIO.
> Depending on packet size, netvsc may attach the buffer as an external
> mbuf. This is not a problem if this mbuf is consumed in the application,
> and the application can correctly read data out of an external mbuf.
> 
> However, there are two problems with data in an external mbuf.
> 1. Due to the limitation of the kernel UIO implementation, physical
> address of this external buffer is not exposed to the user-mode. If this
> mbuf is passed to another driver, the other driver is unable to map this
> buffer to iova.
> 2. Some DPDK applications are not aware of external mbuf, and may bug when
> they receive an mbuf with external buffer attached.
> 
> Introduce a driver parameter "rx_extmbuf_enable" to control if netvsc
> should use external mbuf for receiving packets. The default value is 0.
> (netvsc doesn't use external mbuf, it always allocates mbuf and copy data
> to mbuf) A non-zero value tells netvsc to attach external buffers to mbuf
> on receiving packets, thus avoid copying memory.
> 
> Signed-off-by: Long Li <longli at microsoft.com>
> ---
>   drivers/net/netvsc/hn_ethdev.c | 11 +++++++++++
>   drivers/net/netvsc/hn_rxtx.c   |  2 +-
>   drivers/net/netvsc/hn_var.h    |  3 +++
>   3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/netvsc/hn_ethdev.c b/drivers/net/netvsc/hn_ethdev.c
> index e4f13b962c..735fc6d236 100644
> --- a/drivers/net/netvsc/hn_ethdev.c
> +++ b/drivers/net/netvsc/hn_ethdev.c
> @@ -48,6 +48,7 @@
>   #define NETVSC_ARG_LATENCY "latency"
>   #define NETVSC_ARG_RXBREAK "rx_copybreak"
>   #define NETVSC_ARG_TXBREAK "tx_copybreak"
> +#define NETVSC_ARG_RX_EXTMBUF_ENABLE "rx_extmbuf_enable"
>   

Same comments for with previous patch, can you please document the new devarg 
and 'rte_kvargs_process()' can be used to parse it.



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