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From: Chengchang Tang <tangchengchang@huawei.com>
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	"Yigit, Ferruh" <ferruh.yigit@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Cc: "linuxarm@huawei.com" <linuxarm@huawei.com>,
	"chas3@att.com" <chas3@att.com>,
	"humin29@huawei.com" <humin29@huawei.com>
Subject: Re: [dpdk-dev] [RFC 0/2] add Tx prepare support for bonding device
Date: Tue, 20 Apr 2021 20:44:06 +0800
Message-ID: <04b8a7cd-2563-a7a1-e30a-915da5b2bca3@huawei.com> (raw)
In-Reply-To: <DM6PR11MB4491DA4721949C6D0D56F3729A489@DM6PR11MB4491.namprd11.prod.outlook.com>

Hi
On 2021/4/20 16:33, Ananyev, Konstantin wrote:
> Hi everyone,
> 
>>
>> On 2021/4/20 9:26, Ferruh Yigit wrote:
>>> On 4/16/2021 12:04 PM, Chengchang Tang wrote:
>>>> This patch add Tx prepare for bonding device.
>>>>
>>>> Currently, the bonding driver has not implemented the callback of
>>>> rte_eth_tx_prepare function. Therefore, the TX prepare function of the
>>>> slave devices will never be invoked. When hardware offloading such as
>>>> CKSUM and TSO are enabled for some drivers, tx_prepare needs to be used
>>>> to adjust packets (for example, set correct pseudo packet headers).
>>>> Otherwise, related offloading fails and even packets are sent
>>>> incorrectly. Due to this limitation, the bonded device cannot use these
>>>> HW offloading in the Tx direction.
>>>>
>>>> Because packet sending algorithms are numerous and complex in bond PMD,
>>>> it is hard to design the callback for rte_eth_tx_prepare. In this patch,
>>>> the tx_prepare callback of bonding PMD is not implemented. Instead,
>>>> rte_eth_tx_prepare has been called in tx_burst callback. And a global
>>>> variable is introduced to control whether the bonded device need call
>>>> the rte_eth_tx_prepare. If upper-layer users need to use some TX
>>>> offloading that depend on tx_prepare , they should enable the preparation
>>>> function. In this way, the bonded device will call the rte_eth_tx_prepare
>>>> for the fast path packets in the tx_burst callback.
> 
> I admit that I didn't look at the implementation yet, but it sounds like 
> overcomplication to me. Can't we just have a new TX function for bonding PMD
> when TX offloads are enabled? And inside that function we will do:
> tx_prepare(); tx_burst(); for selected device.

The solution you mentioned is workable and may perform better. However, the current
solution is also simple and has a limited impact on performance. It is actually:
if (tx_prepare_enable)
	tx_prepare();
tx_burst();

Overall, it adds almost only one judgment to the case where the related Tx offloads
is not turned on.

> We can select this function at setup stage analysing requested by user TX offloads. 
> 

In PMDs, it is a common practice to select different Tx/Rx function during the setup
phase. But for a 'vdev' device like Bonding, we may need to think more about it.
The reasons are explained below.
> 
>>>>
>>>
>>> What do you think to add a devarg to bonding PMD to control the tx_prepare?
>>> It won't be as dynamic as API, since it can be possible to change the behavior after application is started with API, but do we really need
>> this?
>>
>> If an API is not added, unnecessary constraints may be introduced. If the
>> bonding device is created through the rte_eth_bond_create interface instead
>> devarg "vdev", this function cannot be used because devargs does not take effect
>> in this case. But from an ease-of-use perspective, adding a devarg is a good
>> idea. I will add related implementations in the later official patches.
> 
> I am also against introducing new devarg to control tx_prepare() invocation.
> I think at dev_config/queue_setup phase PMD will have enough information to decide.
> 
Currently, the community does not specify which Tx offloads need to invoke tx_prepare.
For Vdev devices such as bond, all NIC devices need to be considered. Generally,
tx_prepare is used in CKSUM and TSO. It is possible that for some NIC devices, even
CKSUM and TSO do not need to invoke tx_prepare, or for some NIC devices, there are
other Tx offloads that need to call tx_prepare. From this perspective, leaving the
choice to the user seems to be a better choice.
>>
>> If I understand correctly, the current community does not want to introduce
>> more private APIs for PMDs. However, the absence of an API on this issue would
>> introduce some unnecessary constraints, and from that point of view, I think
>> adding an API seems necessary.
>>>
>>>> Chengchang Tang (2):
>>>>    net/bonding: add Tx prepare for bonding
>>>>    app/testpmd: add cmd for bonding Tx prepare
>>>>
>>>>   app/test-pmd/cmdline.c                      | 66 +++++++++++++++++++++++++++++
>>>>   doc/guides/testpmd_app_ug/testpmd_funcs.rst |  9 ++++
>>>>   drivers/net/bonding/eth_bond_private.h      |  1 +
>>>>   drivers/net/bonding/rte_eth_bond.h          | 29 +++++++++++++
>>>>   drivers/net/bonding/rte_eth_bond_api.c      | 28 ++++++++++++
>>>>   drivers/net/bonding/rte_eth_bond_pmd.c      | 33 +++++++++++++--
>>>>   drivers/net/bonding/version.map             |  5 +++
>>>>   7 files changed, 167 insertions(+), 4 deletions(-)
>>>>
>>>> --
>>>> 2.7.4
>>>>
>>>
>>>
>>> .
>>>
> 


  reply	other threads:[~2021-04-20 12:44 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 11:04 Chengchang Tang
2021-04-16 11:04 ` [dpdk-dev] [RFC 1/2] net/bonding: add Tx prepare for bonding Chengchang Tang
2021-04-16 11:04 ` [dpdk-dev] [RFC 2/2] app/testpmd: add cmd for bonding Tx prepare Chengchang Tang
2021-04-16 11:12 ` [dpdk-dev] [RFC 0/2] add Tx prepare support for bonding device Min Hu (Connor)
2021-04-20  1:26 ` Ferruh Yigit
2021-04-20  2:44   ` Chengchang Tang
2021-04-20  8:33     ` Ananyev, Konstantin
2021-04-20 12:44       ` Chengchang Tang [this message]
2021-04-20 13:18         ` Ananyev, Konstantin
2021-04-20 14:06           ` Chengchang Tang
2021-04-23  9:46 ` [dpdk-dev] [PATCH " Chengchang Tang
2021-04-23  9:46   ` [dpdk-dev] [PATCH 1/2] net/bonding: support Tx prepare for bonding Chengchang Tang
2021-06-08  9:49     ` Andrew Rybchenko
2021-06-09  6:42       ` Chengchang Tang
2021-06-09  9:35         ` Andrew Rybchenko
2021-06-10  7:32           ` Chengchang Tang
2021-06-14 14:16             ` Andrew Rybchenko
2021-06-09 10:25         ` Ananyev, Konstantin
2021-06-10  6:46           ` Chengchang Tang
2021-06-14 11:36             ` Ananyev, Konstantin
2021-04-23  9:46   ` [dpdk-dev] [PATCH 2/2] net/bonding: support configuring Tx offloading " Chengchang Tang
2021-06-08  9:49     ` Andrew Rybchenko
2021-06-09  6:57       ` Chengchang Tang
2021-06-09  9:11         ` Ananyev, Konstantin
2021-06-09  9:37           ` Andrew Rybchenko
2021-06-10  6:29             ` Chengchang Tang
2021-06-14 11:05               ` Ananyev, Konstantin
2021-06-14 14:13                 ` Andrew Rybchenko
2021-04-30  6:26   ` [dpdk-dev] [PATCH 0/2] add Tx prepare support for bonding device Chengchang Tang
2021-04-30  6:47     ` Min Hu (Connor)
2021-06-03  1:44   ` Chengchang Tang

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