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

[Liron Himi]

-----Original Message-----
From: Ferruh Yigit <ferruh.yigit at intel.com> 
Sent: Wednesday, March 13, 2019 18:58
To: Liron Himi <lironh at marvell.com>
Cc: dev at dpdk.org; Alan Winkowski <walan at marvell.com>
Subject: Re: [PATCH v2] net/kni: calc mbuf&mtu according to given mb_pool

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 at intel.com
> Cc: dev at dpdk.org; Liron Himi <lironh at marvell.com>; Liron Himi 
> <lironh at 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 at marvell.com <lironh at marvell.com>
> Sent: Saturday, February 23, 2019 22:15
> To: ferruh.yigit at intel.com
> Cc: dev at dpdk.org; Liron Himi <lironh at marvell.com>
> Subject: [PATCH v2] net/kni: calc mbuf&mtu according to given mb_pool
> 
> From: Liron Himi <lironh at 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?
[L.H.] correct

By providing larger mbuf buffer, it should be possible to send larger (jumbo) packets?
[L.H.] correct

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?
[L.H.] I suggest to first go with this patch, and then prepare multi-segment patch if possible
Multi segment support already exists in userspace to kernel path, but otherway around is missing.

> 
> Signed-off-by: Liron Himi <lironh at 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.
[L.H.] okay

>  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.
[L.H.] okay

Another question, for the case mbuf size < ETHER_MTU, should we keep MTU ETHER_MTU, what do you think?
[L.H.] in any case we need to set the MTU according to the mbuf-size until multi-segment support will be available, right?

>  
>  	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?
[L.H.] 'max_mtu' is set by default to '1500', so in order to be able to modify the interface MTU to support jumbo (or even any size > 1500) the 'max_mtu' must be updated to the larger supported value.