netdev - Re: [PATCH net-next 1/2] pkt_sched: fq: avoid artificial bursts for clocked flows

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Date:	Tue, 3 Feb 2015 19:51:46 +0000
From:	Kenneth Klette Jonassen <kennetkl@....uio.no>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 1/2] pkt_sched: fq: avoid artificial bursts for
 clocked flows


> On 02 Feb 2015, at 20:24, Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> On Mon, 2015-02-02 at 19:59 +0100, Kenneth Klette Jonassen wrote:
>> Current pacing behavior always throttle flows for a time equal to one full
>> quantum, starting at the instance in time when a flow depletes its credit.
>> …
> 
> 
> We do not want to perfectly space packets, but have an efficient packet
> scheduler, allowing TCP pacing.
> 
> I chose to not use ktime_get() in enqueue() when I wrote sch_fq.
Posted V2 to address this.

> 
> A Token Bucket Filter has the notion of quantum, meaning you configure
> the granularity given this quantum.
> 
> At Google, we have a special handling for TCP ACK packets, so that they
> do not interfere with FQ/pacing.
Interesting. How does this work when ACKs are piggybacked to data?

> 
> ACK packets are not paced, ever.
> 
> This patch also allows skb->ooo_okay being set even if the DATA packet
> immediately follows a train of ACK packets (as in typical RPC patterns)
> 
Could you please expand on this?

Thanks for the feedback so far.

Sincerely,
Kenneth