netdev - Re: [PATCH bpf-next v7 00/13] net-timestamp: bpf extension to equip applications transparently

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Message-ID: <CAL+tcoBiRrB+_p=W-EwRL-Dqa2kWY-yAWTNurbpF10DG96=Q6Q@mail.gmail.com>
Date: Wed, 5 Feb 2025 02:12:19 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, dsahern@...nel.org, willemb@...gle.com, 
	ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, eddyz87@...il.com, 
	song@...nel.org, yonghong.song@...ux.dev, john.fastabend@...il.com, 
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org, 
	horms@...nel.org, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v7 00/13] net-timestamp: bpf extension to equip
 applications transparently

On Wed, Feb 5, 2025 at 1:11 AM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Jason Xing wrote:
> > On Tue, Feb 4, 2025 at 10:27 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
> > >
> > > On 1/28/25 12:46 AM, Jason Xing wrote:
> > > > "Timestamping is key to debugging network stack latency. With
> > > > SO_TIMESTAMPING, bugs that are otherwise incorrectly assumed to be
> > > > network issues can be attributed to the kernel." This is extracted
> > > > from the talk "SO_TIMESTAMPING: Powering Fleetwide RPC Monitoring"
> > > > addressed by Willem de Bruijn at netdevconf 0x17).
> > > >
> > > > There are a few areas that need optimization with the consideration of
> > > > easier use and less performance impact, which I highlighted and mainly
> > > > discussed at netconf 2024 with Willem de Bruijn and John Fastabend:
> > > > uAPI compatibility, extra system call overhead, and the need for
> > > > application modification. I initially managed to solve these issues
> > > > by writing a kernel module that hooks various key functions. However,
> > > > this approach is not suitable for the next kernel release. Therefore,
> > > > a BPF extension was proposed. During recent period, Martin KaFai Lau
> > > > provides invaluable suggestions about BPF along the way. Many thanks
> > > > here!
> > > >
> > > > In this series, I only support foundamental codes and tx for TCP.
> > >
> > > *fundamental*.
> > >
> > > May be just "only tx time stamping for TCP is supported..."
> > >
> > > > This approach mostly relies on existing SO_TIMESTAMPING feature, users
> > > > only needs to pass certain flags through bpf_setsocktopt() to a separate
> > > > tsflags. Please see the last selftest patch in this series.
> > > >
> > > > After this series, we could step by step implement more advanced
> > > > functions/flags already in SO_TIMESTAMPING feature for bpf extension.
> > >
> > > Patch 1-4 and 6-11 can use an extra "bpf:" tag in the subject line. Patch 13
> > > should be "selftests/bpf:" instead of "bpf:" in the subject.
> > >
> > > Please revisit the commit messages of this patch set to check for outdated
> > > comments from the earlier revisions. I may have missed some of them.
> >
> > Roger that, sir. Thanks for your help!
> >
> > >
> > > Overall, it looks close. I will review at your replies later.
> > >
> > > Willem, could you also take a look? Thanks.
> >
> > Right, some related parts need reviews from netdev experts as well.
> >
> > Willem, please help me review this when you're available. No rush :)
>
> I won't have much to add for the BPF side, to be clear.
>
> One small high level commit message point: as submitting-patches
> suggests, use imperative mood: "adds X" when the patch introduces a
> feature, not "I add". And "caller gets" rather than "we get".
>
> Specific case, with capitalization issue: "we need to Introduce".

Thanks for learning a new lesson. I will adjust them.

>
> I'll respond to a few inline code elements later. Nothing huge.
> Also feel free to post the next version and I'll respond to that, if
> you prefer.

I will post v8 soon. Thanks for your precious time. Have fun with your trip :p

Thanks,
Jason