linux-kernel - Re: [PATCH RFC v2 net-next 0/5] net: Qdisc backpressure infrastructure

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Message-ID: <20220829172111.4471d913@kernel.org>
Date:   Mon, 29 Aug 2022 17:21:11 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Peilin Ye <yepeilin.cs@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Peilin Ye <peilin.ye@...edance.com>, netdev@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Cong Wang <cong.wang@...edance.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Dave Taht <dave.taht@...il.com>
Subject: Re: [PATCH RFC v2 net-next 0/5] net: Qdisc backpressure
 infrastructure

On Mon, 29 Aug 2022 09:53:17 -0700 Cong Wang wrote:
> > Similarly to Eric's comments on v1 I'm not seeing the clear motivation
> > here. Modern high speed UDP users will have a CC in user space, back
> > off and set transmission time on the packets. Could you describe your
> > _actual_ use case / application in more detail?  
> 
> Not everyone implements QUIC or CC, it is really hard to implement CC
> from scratch. This backpressure mechnism is much simpler than CC (TCP or
> QUIC), as clearly it does not deal with any remote congestions.
> 
> And, although this patchset only implements UDP backpressure, it can be
> applied to any other protocol easily, it is protocol-independent.

No disagreement on any of your points. But I don't feel like 
you answered my question about the details of the use case.