netdev - Re: One question about __tcp_select

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Message-ID: <CAP4sYWVGnG_cJyZxY2JQGz6+0+PRxkrZTarHFRuU6qjNvLA_bw@mail.gmail.com>
Date:   Wed, 18 Apr 2018 08:23:44 +0800
From:   Wang Jian <jianjian.wang1@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: One question about __tcp_select_window()

Thanks for your reply, Eric.

Actually, this is a query about the code while I am reading code.
>From my instinct and the comment, I think we should choose the bigger
one but maybe I miss something(like your said, autotuning)
Anyway, I will read more codes and do more tests.

Thanks.

On Tue, Apr 17, 2018 at 10:43 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>
> On 04/17/2018 06:53 AM, Wang Jian wrote:
>> I test the fix with 4.17.0-rc1+ and it seems work.
>>
>> 1. iperf -c IP -i 20 -t 60 -w 1K
>>  with-fix vs without-fix : 1.15Gbits/sec vs 1.05Gbits/sec
>> I also try other windows and have similar results.
>>
>> 2. Use tcp probe trace snd_wind.
>> with-fix vs without-fix: 1245568 vs 1042816
>>
>> 3. I don't see extra retransmit/drops.
>>
>
> Unfortunately I have no idea what exact problem you had to solve.
>
> Setting small windows is not exactly the path we are taking.
>
> And I do not know how many side effects your change will have for 'standard' flows
> using autotuning or sane windows.
>