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

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Message-ID: <67a2491090b3c_bb56629464@willemb.c.googlers.com.notmuch>
Date: Tue, 04 Feb 2025 12:06:24 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>, 
 Jason Xing <kerneljasonxing@...il.com>
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

Martin KaFai Lau 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.
> 
> Overall, it looks close. I will review at your replies later.
> 
> Willem, could you also take a look? Thanks.

Will do. Traveling, but took a first quick skim.