netdev - Re: [PATCH net-next v2 05/10] net: qualcomm: rmnet: Set pacing rate

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Date:   Wed, 03 Jan 2018 23:44:50 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, lkp@...el.com
Subject: Re: [PATCH net-next v2 05/10] net: qualcomm: rmnet: Set pacing rate

On Wed, 2018-01-03 at 15:45 -0700, Subash Abhinov Kasiviswanathan
wrote:
> > > +	sk_pacing_shift_update(skb->sk, 8);
> > 
> > Well... Please tell us why this is needed in this driver.
> > 
> > This interface is meant for wifi aggregation, not to work around some
> > strange ethernet drivers designs.
> 
> Hi Eric
> 
> The real device over which the rmnet devices are installed also
> aggregate multiple IP packets and sends them as a single large aggregate
> frame to the hardware.

It would be nice to give some details about this in the changelog.

Also what results you get with different values for the shift (10, 9,
8)

My fear is that people might be tempted to blindly use the
sk_pacing_shift_update() just because a single TCP flow gets 'better'
results.

bufferbloat is a serious issue, we do not want to allow a single TCP
flow to fill a fifo.

Otherwise, we could remove TCP Small queues overhead from the kernel
and be happy.

Thanks.