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Date: Fri, 05 May 2017 06:52:26 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: 单卫 <shanwei88@...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
On Fri, 2017-05-05 at 18:22 +0800, 单卫 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.
>
> 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 ?
We want to make autotuning better, so that tweaks like that are no
longer needed.
>
>
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