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

["Zhang, Qi Z" <qi.z.zhang@intel.com>]

> -----Original Message-----
> From: Kevin Traynor <ktraynor@redhat.com>
> Sent: Thursday, March 24, 2022 8:18 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 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.

OK, I updated with below commit log in dpdk-next-net-intel.
Kevin , Wenjun, let me know if anything I missed.

    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.

    The patch proved a 50% ~ 70% single core performance improvement on a
    main stream Xeon server, and it is necessary to be backport to LTS release,
    as this fix the performance gap for some use cases.

Thanks
Qi

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