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From: Simon Barber <simon@superduper.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Dave Taht <dave.taht@gmail.com>,
	Make-Wifi-fast <make-wifi-fast@lists.bufferbloat.net>,
	Johannes Berg <johannes@sipsolutions.net>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Neal Cardwell <ncardwell@google.com>,
	Netdev <netdev@vger.kernel.org>
Subject: Re: [Make-wifi-fast] debugging TCP stalls on high-speed wifi
Date: Thu, 12 Dec 2019 17:57:13 -0800	[thread overview]
Message-ID: <5DBB113A-E61A-4032-B877-18BE3ABBC616@superduper.net> (raw)
In-Reply-To: <34a05f62-8dd0-9ea0-2192-1da5bfe6d843@gmail.com>

In my application this is a bridge or router (not TCP endpoint), and the driver is doing GRO and NAPI polling. Also looking at using the skb->fraglist to make the GRO code more effective and more transparent by passing flags, short segments, etc through for perfect reconstruction by TSO.

Simon

> On Dec 12, 2019, at 5:46 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> 
> 
> 
> On 12/12/19 4:59 PM, Simon Barber wrote:
>> I’m currently adding ACK thinning to Linux’s GRO code. Quite a simple addition given the way that code works.
>> 
>> Simon
>> 
>> 
> 
> Please don't.
> 
> 1) It will not help since many NIC  do not use GRO.
> 
> 2) This does not help if you receive one ACK per NIC interrupt, which is quite common.
> 
> 3) This breaks GRO transparency.
> 
> 4) TCP can implement this in a more effective/controlled way,
>   since the peer know a lot more flow characteristics.
> 
> Middle-box should not try to make TCP better, they usually break things.


  reply	other threads:[~2019-12-13  1:57 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <14cedbb9300f887fecc399ebcdb70c153955f876.camel@sipsolutions.net>
     [not found] ` <CADVnQym_CNktZ917q0-9dVY9dhtiJVRRotGTrPNdZUpkjd3vyw@mail.gmail.com>
     [not found]   ` <f4670ce0f4399fe82e7168fb9c491d8eb718e8d8.camel@sipsolutions.net>
     [not found]     ` <99748db5-7898-534b-d407-ed819f07f939@gmail.com>
     [not found]       ` <ff6b35ad589d7cf0710cb9fca4c799538da2e653.camel@sipsolutions.net>
2019-12-12 23:42         ` Dave Taht
2019-12-13  0:59           ` Simon Barber
2019-12-13  1:46             ` Eric Dumazet
2019-12-13  1:57               ` Simon Barber [this message]
2019-12-13  4:42               ` Dave Taht
2019-12-13  8:08           ` Johannes Berg

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