Re: [dpdk-dev] [PATCH v2] net/kni: calc mbuf&mtu according to given mb_pool

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/10/2019 2:27 PM, Liron Himi wrote:
> Adding Alan.
> 
> -----Original Message-----
> From: Liron Himi 
> Sent: Monday, February 25, 2019 13:30
> To: ferruh.yigit@intel.com
> Cc: dev@dpdk.org; Liron Himi <lironh@marvell.com>; Liron Himi <lironh@marvell.com>
> Subject: RE: [PATCH v2] net/kni: calc mbuf&mtu according to given mb_pool
> 
> Hi,
> 
> Kind reminder

Sorry for late response.

> 
> Regards,
> Liron
> 
> -----Original Message-----
> From: lironh@marvell.com <lironh@marvell.com>
> Sent: Saturday, February 23, 2019 22:15
> To: ferruh.yigit@intel.com
> Cc: dev@dpdk.org; Liron Himi <lironh@marvell.com>
> Subject: [PATCH v2] net/kni: calc mbuf&mtu according to given mb_pool
> 
> From: Liron Himi <lironh@marvell.com>
> 
> - mbuf_size and mtu are now being calculated according to the given mb-pool.

+1 to have dynamic size instead of fixed "MAX_PACKET_SZ"

> 
> - max_mtu is now being set according to the given mtu
> 
> the above two changes provide the ability to work with jumbo frames

>From kernel -> userspace, if the data length is bigger than mbuf->buffer_len (-
headroom) the packet is dropped. I guess you are trying to solve that issue?

By providing larger mbuf buffer, it should be possible to send larger (jumbo)
packets?

Another option can be adding multi segment send support, that also lets sending
large packets from kernel to userspace, and it can co-exits with your patch.
What do you think, can you work on that support?
Multi segment support already exists in userspace to kernel path, but otherway
around is missing.

> 
> Signed-off-by: Liron Himi <lironh@marvell.com>
> ---
>  drivers/net/kni/rte_eth_kni.c | 10 +++++++---
>  kernel/linux/kni/compat.h     |  4 ++++
>  kernel/linux/kni/kni_misc.c   |  3 +++

It can be good to update release notes / kni documentation to document new feature.

>  3 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/kni/rte_eth_kni.c b/drivers/net/kni/rte_eth_kni.c index a1e9970..5e02224 100644
> --- a/drivers/net/kni/rte_eth_kni.c
> +++ b/drivers/net/kni/rte_eth_kni.c
> @@ -16,9 +16,11 @@
>  /* Only single queue supported */
>  #define KNI_MAX_QUEUE_PER_PORT 1
>  
> -#define MAX_PACKET_SZ 2048
>  #define MAX_KNI_PORTS 8
>  
> +#define KNI_ETHER_MTU(mbuf_size)       \
> +	((mbuf_size) - ETHER_HDR_LEN) /**< Ethernet MTU. */
> +
>  #define ETH_KNI_NO_REQUEST_THREAD_ARG	"no_request_thread"
>  static const char * const valid_arguments[] = {
>  	ETH_KNI_NO_REQUEST_THREAD_ARG,
> @@ -123,11 +125,13 @@ eth_kni_start(struct rte_eth_dev *dev)
>  	struct rte_kni_conf conf;
>  	const char *name = dev->device->name + 4; /* remove net_ */
>  
> +	mb_pool = internals->rx_queues[0].mb_pool;
>  	snprintf(conf.name, RTE_KNI_NAMESIZE, "%s", name);
>  	conf.force_bind = 0;
>  	conf.group_id = port_id;
> -	conf.mbuf_size = MAX_PACKET_SZ;
> -	mb_pool = internals->rx_queues[0].mb_pool;
> +	conf.mbuf_size =
> +		rte_pktmbuf_data_room_size(mb_pool) - RTE_PKTMBUF_HEADROOM;
> +	conf.mtu = KNI_ETHER_MTU(conf.mbuf_size);

Can you please do "conf.mbuf_size" changes also to kni sample application?
kni sample application gets mtu from physical device, so I believe better to not
change that but I think mbuf_size can be dynamic instead of hardcoded.

Another question, for the case mbuf size < ETHER_MTU, should we keep MTU
ETHER_MTU, what do you think?

>  
>  	internals->kni = rte_kni_alloc(mb_pool, &conf, NULL);
>  	if (internals->kni == NULL) {
> diff --git a/kernel/linux/kni/compat.h b/kernel/linux/kni/compat.h index 3c575c7..b9f9a6f 100644
> --- a/kernel/linux/kni/compat.h
> +++ b/kernel/linux/kni/compat.h
> @@ -117,3 +117,7 @@
>  #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 11, 0)  #define HAVE_SIGNAL_FUNCTIONS_OWN_HEADER  #endif
> +
> +#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 10, 0) #define 
> +HAVE_MAX_MTU_PARAM #endif
> diff --git a/kernel/linux/kni/kni_misc.c b/kernel/linux/kni/kni_misc.c index 522ae23..04c78eb 100644
> --- a/kernel/linux/kni/kni_misc.c
> +++ b/kernel/linux/kni/kni_misc.c
> @@ -459,6 +459,9 @@ kni_ioctl_create(struct net *net, uint32_t ioctl_num,
>  
>  	if (dev_info.mtu)
>  		net_dev->mtu = dev_info.mtu;
> +#ifdef HAVE_MAX_MTU_PARAM
> +	net_dev->max_mtu = net_dev->mtu;
> +#endif

Do we need to set 'max_mtu'? I guess this is not really required for large
packet support, if so what do you think making this separate patch?