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

[Liron Himi <lironh@marvell.com>]

-----Original Message-----
From: Ferruh Yigit <ferruh.yigit@intel.com> 
Sent: Friday, March 15, 2019 19:59
To: Liron Himi <lironh@marvell.com>
Cc: dev@dpdk.org; Alan Winkowski <walan@marvell.com>
Subject: Re: [PATCH v2] net/kni: calc mbuf&mtu according to given mb_pool

On 3/15/2019 5:02 PM, Liron Himi wrote:
> 
> 
> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Thursday, March 14, 2019 11:28
> To: Liron Himi <lironh@marvell.com>
> Cc: dev@dpdk.org; Alan Winkowski <walan@marvell.com>
> Subject: Re: [PATCH v2] net/kni: calc mbuf&mtu according to given 
> mb_pool
> 
> On 3/14/2019 6:37 AM, Liron Himi wrote:
>>
>>
>> -----Original Message-----
>> From: Ferruh Yigit <ferruh.yigit@intel.com>
>> Sent: Wednesday, March 13, 2019 18:58
>> To: Liron Himi <lironh@marvell.com>
>> Cc: dev@dpdk.org; Alan Winkowski <walan@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@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?
>> [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
> 
> Yes, I was hoping both can go in a same patchset, can it be possible?
> [L.H.] I'm on tight schedule right now, I prefer to continue with  this patch as is, multi-segment support can be pushed later on.

OK

> 
>> 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.
>> [L.H.] okay
[L.H.] I have made the following change, but I'm not sure to which document to mark the adding of this new feature.
Is it release notes? If yes, which exact one? 

Should I mark it as Jumbo support? Or just specify that the mtu and mbuf are based on the given pool?


diff --git a/doc/guides/nics/kni.rst b/doc/guides/nics/kni.rst
index 204fbd5..a66c595 100644
--- a/doc/guides/nics/kni.rst
+++ b/doc/guides/nics/kni.rst
@@ -55,7 +55,8 @@ configuration:
 
         Interface name: kni#
         force bind kernel thread to a core : NO
-        mbuf size: MAX_PACKET_SZ
+        mbuf size: (rte_pktmbuf_data_room_size(pktmbuf_pool) - RTE_PKTMBUF_HEADROOM)
+        mtu: (conf.mbuf_size - ETHER_HDR_LEN)
>>
>>>  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?
> 
> 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.
> 
> I missed that it set by default to '1500', I was thinking it is zero by default.
> Can you please point where its default value set in Linux?
> [L.H.] I also thought that a zero value will make more sense to provide backwards compatibility, but this is not the case.
> Here is the code snipped from net/ethernet/eth.c :
> void ether_setup(struct net_device *dev) {
> 	dev->header_ops		= &eth_header_ops;
> 	dev->type		= ARPHRD_ETHER;
> 	dev->hard_header_len 	= ETH_HLEN;
> 	dev->min_header_len	= ETH_HLEN;
> 	dev->mtu		= ETH_DATA_LEN;
> 	dev->min_mtu		= ETH_MIN_MTU;
> 	dev->max_mtu		= ETH_DATA_LEN;
> 

You are right, thanks for the pointer, please go with this update.