netdev - Re: OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] fq_codel

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Date:	Mon, 16 May 2016 02:27:09 +0300
From:	Roman Yeryomin <leroi.lists@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Dave Taht <dave.taht@...il.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Felix Fietkau <nbd@....name>,
	Jonathan Morton <chromatix99@...il.com>,
	"codel@...ts.bufferbloat.net" <codel@...ts.bufferbloat.net>,
	ath10k <ath10k@...ts.infradead.org>,
	make-wifi-fast@...ts.bufferbloat.net,
	Rafał Miłecki <zajec5@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	OpenWrt Development List <openwrt-devel@...ts.openwrt.org>,
	Michal Kazior <michal.kazior@...to.com>
Subject: Re: OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel]
 fq_codel_drop vs a udp flood)

On 16 May 2016 at 02:07, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Mon, 2016-05-16 at 01:34 +0300, Roman Yeryomin wrote:
>
>> qdisc fq_codel 8003: parent :3 limit 1024p flows 16 quantum 1514
>> target 80.0ms ce_threshold 32us interval 100.0ms ecn
>>  Sent 1601271168 bytes 1057706 pkt (dropped 1422304, overlimits 0 requeues 17)
>>  backlog 1541252b 1018p requeues 17
>>   maxpacket 1514 drop_overlimit 1422304 new_flow_count 35 ecn_mark 0
>>   new_flows_len 0 old_flows_len 1
>
> Why do you have ce_threshold set ? You really should not (even if it
> does not matter for the kind of traffic you have at this moment)

No idea, it was there always. How do I unset it? Setting it to 0 doesn't help.

> If your expected link speed is around 1Gbps, or 80,000 packets per
> second, then you have to understand that 1024 packets limit is about 12
> ms at most.
>
> Even if the queue is full, max sojourn time of a packet would be 12 ms.
>
> I really do not see how 'target 80 ms' could be hit.

Well, as I said, I've tried different options. Neither target 20ms (as
Dave proposed) not 12ms save the situation.

> You basically have FQ, with no Codel effect, but with the associated
> cost of Codel (having to take timestamps)
>
>
>