netdev - Re: [PATCH] tcp: remove obsolete paramter sysctl_tcp_low

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Message-ID: <20210107090635.440b1fc6@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 7 Jan 2021 09:06:35 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     lll <liyonglong@...natelecom.cn>
Cc:     Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        davem@...emloft.net, fw@...len.de, soheil@...gle.com,
        ncardwell@...gle.com, ycheng@...gle.com
Subject: Re: [PATCH] tcp: remove obsolete paramter sysctl_tcp_low_latency

On Thu, 7 Jan 2021 11:08:16 +0800 lll wrote:
> 在 2020/12/19 8:46, Jakub Kicinski 写道:
> > On Fri, 18 Dec 2020 14:11:16 +0800 lyl wrote:  
> >> Remove tcp_low_latency, since it is not functional After commit
> >> e7942d0633c4 (tcp: remove prequeue support)
> >>
> >> Signed-off-by: lyl <liyonglong@...natelecom.cn>  
> > 
> > I don't think we can remove sysctls, even if they no longer control 
> > the behavior of the kernel. The existence of the file itself is uAPI.
>
> Got it. But a question: why tcp_tw_recycle can be removed totally?
> it is also part of uAPI

Good question, perhaps with tcp_tw_recycle we wanted to make sure users
who depended on it notice removal, since the feature was broken by
design? 

tcp_low_latency is an optimization, not functionality which users may
depend on.

But I may be wrong so CCing authors.