Re: [PATCH v4] net/ice: improve performance of RX timestamp offload

[Kevin Traynor <ktraynor@redhat.com>]

On 24/03/2022 11:51, Zhang, Qi Z wrote:
> 
> 
>> -----Original Message-----
>> From: Kevin Traynor <ktraynor@redhat.com>
>> Sent: Thursday, March 24, 2022 7:17 PM
>> To: Zhang, Qi Z <qi.z.zhang@intel.com>; Wu, Wenjun1
>> <wenjun1.wu@intel.com>; dev@dpdk.org; Yang, Qiming
>> <qiming.yang@intel.com>
>> Cc: Van Haaren, Harry <harry.van.haaren@intel.com>; Su, Simei
>> <simei.su@intel.com>; Luca Boccassi <bluca@debian.org>; Christian Ehrhardt
>> <christian.ehrhardt@canonical.com>
>> Subject: Re: [PATCH v4] net/ice: improve performance of RX timestamp
>> offload
>>
>> On 24/03/2022 09:09, Zhang, Qi Z wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: Wu, Wenjun1 <wenjun1.wu@intel.com>
>>>> Sent: Monday, February 28, 2022 3:36 PM
>>>> To: dev@dpdk.org; Zhang, Qi Z <qi.z.zhang@intel.com>; Yang, Qiming
>>>> <qiming.yang@intel.com>
>>>> Cc: Van Haaren, Harry <harry.van.haaren@intel.com>; Su, Simei
>>>> <simei.su@intel.com>; Wu, Wenjun1 <wenjun1.wu@intel.com>
>>>> Subject: [PATCH v4] net/ice: improve performance of RX timestamp
>>>> offload
>>>>
>>>> Previously, each time a burst of packets is received, SW reads HW
>>>> register and assembles it and the timestamp from descriptor together
>>>> to get the complete 64 bits timestamp.
>>>>
>>>> This patch optimizes the algorithm. The SW only needs to check the
>>>> monotonicity of the low 32bits timestamp to avoid crossing borders.
>>>> Each time before SW receives a burst of packets, it should check the
>>>> time difference between current time and last update time to avoid
>>>> the low 32 bits timestamp cycling twice.
>>>>
>>>> Signed-off-by: Wenjun Wu <wenjun1.wu@intel.com>
>>>
>>> Added cc stable
>>>
>>
>> Hi Qi. The DPDK documentation has guidance about what should be
>> backported to LTS [0] and distinguishes between fixes and performance
>> improvements. Please try and stick with this when applying patches or let LTS
>> maintainers know if there is a debatable case.
> 
> Thanks for the comments
> Yes, actually this is about a 50% ~ 70% performance improvement, which maybe critical for some performance sensitive use cases.(e.g. network forensics)
> So I'd like to defend with below case
> 
> An existing feature in LTS is not usable as intended without it.
> 

If that is the case, then I think the commitlog should be re-written. It 
just talks about the code changes, there's nothing about an impact to an 
existing use case that was unusuable and is now fixed.

> Thanks
> Qi
> 
>>
>> thanks,
>> Kevin.
>>
>> [0]
>> http://doc.dpdk.org/guides-21.11/contributing/stable.html#what-changes-
>> should-be-backported
> 
>>
>>> Acked-by: Qi Zhang <qi.z.zhang@intel.com>
>>>
>>> Applied to dpdk-next-net-intel.
>>>
>>> Thanks
>>> Qi
>>>
>>
>