netdev - Re: [PATCH net-next ] tcp: add new parameter tcp_inherit_buffsize to control the initial buffer size for new passive connetion

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Date:   Mon, 8 May 2017 15:49:41 +0800
From:   Shan Wei <shanwei88@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev <netdev@...r.kernel.org>, David Miller <davem@...emloft.net>
Subject: Re: [PATCH net-next ] tcp: add new parameter tcp_inherit_buffsize to
 control the initial buffer size for new passive connetion

at 2017/5/5 21:52
> On Fri, 2017-05-05 at 18:22 +0800,  wrote:
>>
>> 2017-05-02 23:05 GMT+08:00 Eric Dumazet <eric.dumazet@...il.com>:
>>         
>>         
>>         Hi Shan
>>         
>>         1) Your patch never reached netdev, because it was sent in
>>         HTML format.
>>         
>>         2) During Linus merge window, net-next is closed
>>         
>>         I am not really convinced that we need this with TCP
>>         autotuning anyway.
>>         Initial value of sk_sndbuf and sk_rcvbuf is really a hint.
>>         
>>         How often do you really tweak /proc/sys/net/ipv4 files in
>>         production.
>>
>>
>>
> Again you posted your reply in HTML, so netdev did not get it.
Now, fix it with thunderbird instead of gmail web client.
>> Historically, most products have not adjusted any wmem/rmem
>> parameters.
>> In our experience to adjust the parameters, you can get a better visit
>> experience, faster. 
>>
>> Now more and more products want to change this default value.
>> But for a product, once we adjust the parameters, it is rarely
>> adjusted.
>>
>>
>> We hope that this patch can provide a capacity: adjust the parameters
>> online and quickly take effect.
>>
>> Without this patch, it is time consuming for us to adjust the
>> parameters and need to migrate flows.
>>
>>
>>
>>          
>>         Please provide more information, like what actual values you
>>         change back
>>         and forth.
>>         
>>
>>
>> There is no a fixed value here. big value, will take up more memory
>> resources.
>> But we are also willing to sacrifice memory for performance.
>>
>> Select the parameter value based on the characteristics of the
>> product.
>>
>> For example, for 1MB files, we will set buffsize to 1611646 = (1MB /
>> 1460) * 2244
>> Mss = 1460, SKB_TRUESIZE = 2244
>>
>>
>> With TCP autotuning, reach the buffer size until the cwnd equal 359
>> from 10.
> Looks like a problem with autotuning because you might have HZ=100 or
> HZ=250 maybe ?
Indeed,  HZ=250.  What is the problem about autotuning with HZ=250?