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

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Message-ID: <CAL+tcoAXcDuAsy6rqGBh3Sb1dkdZ0xn6YFCQec-K6QSPyaVwEA@mail.gmail.com>
Date: Tue, 4 Feb 2025 10:44:59 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, willemdebruijn.kernel@...il.com, 
	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 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 :)

Thanks,
Jason