netdev - Re: [PATCH net-next 0/2] add more drop reasons in tcp receive path

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Message-ID: <CAL+tcoA2vGwOgFj_kHYEmaDxXBt0c-bfBiXeqYYhgh6zWO5w9A@mail.gmail.com>
Date: Thu, 8 Feb 2024 08:48:02 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	dsahern@...nel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next 0/2] add more drop reasons in tcp receive path

On Wed, Feb 7, 2024 at 9:37 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Wed, Feb 7, 2024 at 2:25 PM Jason Xing <kerneljasonxing@...il.com> wrote:
> >
>
> > Indeed.
> >
> > It took me some while to consider whether I should add more reasons
> > into the fast path.
> >
> > But for now the NOT_SPECIFIED fake reason does not work if we really
> > want to know some useful hints.
> > What do you think? Should I give up this patch series or come up with
> > other better ideas?
>
> Perhaps find a way to reuse return values from functions to carry a drop_reason.

It seems feasible to reuse return values, let me work on it :)

>
> >
> > >
> > > Please make sure not to slow down the TCP fast path, while we work
> > > hard in the opposite direction.
> >
> > I tested some times by using netperf, it's not that easy to observe
> > the obvious differences before/after this patch applied.
>
> Sure, the difference is only noticeable on moderate load, when a cpu
> receives one packet in a while.
>
> icache pressure, something hard to measure with synthetic benchmarks,
> but visible in real workloads in the long term.
>
> At Google, we definitely see an increase of network cpu costs releases
> after releases.

Thanks for your explanations.

Thanks,
Jason