From: Dave Taht <dave.taht@gmail.com>
To: Jonathan Morton <chromatix99@gmail.com>
Cc: make-wifi-fast@lists.bufferbloat.net,
"codel@lists.bufferbloat.net" <codel@lists.bufferbloat.net>,
ath10k <ath10k@lists.infradead.org>,
Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [Codel] fq_codel_drop vs a udp flood
Date: Mon, 2 May 2016 19:26:45 -0700 [thread overview]
Message-ID: <CAA93jw6WKyWmgzni1Tn0oQfJyN7hss++MKLkJ8+3sRcVLu7krg@mail.gmail.com> (raw)
In-Reply-To: <865DA393-262D-40B6-A9D3-1B978CD5F6C6@gmail.com>
On Sun, May 1, 2016 at 11:20 AM, Jonathan Morton <chromatix99@gmail.com> wrote:
>
>> On 1 May, 2016, at 20:59, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>>
>> fq_codel_drop() could drop _all_ packets of the fat flow, instead of a
>> single one.
>
> Unfortunately, that could have bad consequences if the “fat flow” happens to be a TCP in slow-start on a long-RTT path. Such a flow is responsive, but on an order-magnitude longer timescale than may have been configured as optimum.
>
> The real problem is that fq_codel_drop() performs the same (excessive) amount of work to cope with a single unresponsive flow as it would for a true DDoS. Optimising the search function is sufficient.
Don't think so.
I did some tests today, (not the fq_codel batch drop patch yet)
When hit with a 900mbit flood, cake shaping down to 250mbit, results
in nearly 100% cpu use in the ksoftirq1 thread on the apu2, and
150mbits of actual throughput (as measured by iperf3, which is now a
measurement I don't trust)
cake *does* hold the packet count down a lot better than fq_codel does.
fq_codel (pre eric's patch) basically goes to the configured limit and
stays there.
In both cases I will eventually get an error like this (in my babel
routed environment) that suggests that we're also not delivering
packets from other flows (arp?) with either fq_codel or cake in these
extreme conditions.
iperf3 -c 172.26.64.200 -u -b900Mbit -t 600
[ 4] 47.00-48.00 sec 107 MBytes 895 Mbits/sec 13659
iperf3: error - unable to write to stream socket: No route to host
...
The results I get from iperf are a bit puzzling over the interval it
samples at - this is from a 100Mbit test (downshifting from 900mbit)
[ 15] 25.00-26.00 sec 152 KBytes 1.25 Mbits/sec 0.998 ms
29673/29692 (1e+02%)
[ 15] 26.00-27.00 sec 232 KBytes 1.90 Mbits/sec 1.207 ms
10235/10264 (1e+02%)
[ 15] 27.00-28.00 sec 72.0 KBytes 590 Kbits/sec 1.098 ms
19035/19044 (1e+02%)
[ 15] 28.00-29.00 sec 0.00 Bytes 0.00 bits/sec 1.098 ms 0/0 (-nan%)
[ 15] 29.00-30.00 sec 72.0 KBytes 590 Kbits/sec 1.044 ms
22468/22477 (1e+02%)
[ 15] 30.00-31.00 sec 64.0 KBytes 524 Kbits/sec 1.060 ms
13078/13086 (1e+02%)
[ 15] 31.00-32.00 sec 0.00 Bytes 0.00 bits/sec 1.060 ms 0/0 (-nan%)
^C[ 15] 32.00-32.66 sec 64.0 KBytes 797 Kbits/sec 1.050 ms
25420/25428 (1e+02%)
Not that I care all that much about how iperf is intepreting it's drop
rate (I guess pulling apart the actual caps is in order).
As for cake struggling to cope:
root@apu2:/home/d/git/tc-adv/tc# ./tc -s qdisc show dev enp2s0
qdisc cake 8018: root refcnt 9 bandwidth 100Mbit diffserv4 flows rtt 100.0ms raw
Sent 219736818 bytes 157121 pkt (dropped 989289, overlimits 1152272 requeues 0)
backlog 449646b 319p requeues 0
memory used: 2658432b of 5000000b
capacity estimate: 100Mbit
Bulk Best Effort Video Voice
thresh 100Mbit 93750Kbit 75Mbit 25Mbit
target 5.0ms 5.0ms 5.0ms 5.0ms
interval 100.0ms 100.0ms 100.0ms 100.0ms
pk_delay 0us 5.2ms 92us 48us
av_delay 0us 5.1ms 4us 2us
sp_delay 0us 5.0ms 4us 2us
pkts 0 1146649 31 49
bytes 0 1607004053 2258 8779
way_inds 0 0 0 0
way_miss 0 15 2 1
way_cols 0 0 0 0
drops 0 989289 0 0
marks 0 0 0 0
sp_flows 0 0 0 0
bk_flows 0 1 0 0
last_len 0 1514 66 138
max_len 0 1514 110 487
...
But I am very puzzled as to why flow isolation would fail in the face
of this overload.
> - Jonathan Morton
>
--
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org
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next prev parent reply other threads:[~2016-05-03 2:27 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-01 3:41 fq_codel_drop vs a udp flood Dave Taht
2016-05-01 4:46 ` [Make-wifi-fast] " Jonathan Morton
2016-05-01 5:08 ` Ben Greear
2016-05-01 5:23 ` Dave Taht
2016-05-01 14:47 ` [Make-wifi-fast] " dpreed
2016-05-02 14:03 ` Roman Yeryomin
2016-05-02 18:40 ` Dave Taht
2016-05-05 13:55 ` Roman Yeryomin
2016-05-05 14:55 ` Roman Yeryomin
2016-05-02 19:47 ` David Lang
2016-05-01 17:59 ` [Codel] " Eric Dumazet
2016-05-01 18:20 ` Jonathan Morton
2016-05-01 18:46 ` Eric Dumazet
2016-05-01 19:55 ` Eric Dumazet
2016-05-02 7:47 ` Jesper Dangaard Brouer
2016-05-01 20:35 ` Jonathan Morton
2016-05-01 20:55 ` Eric Dumazet
2016-05-02 14:18 ` Roman Yeryomin
2016-05-02 15:07 ` Eric Dumazet
2016-05-02 15:43 ` Roman Yeryomin
2016-05-02 16:14 ` Eric Dumazet
2016-05-02 17:08 ` Dave Taht
2016-05-02 17:44 ` Eric Dumazet
2016-05-05 14:32 ` Roman Yeryomin
2016-05-05 14:53 ` Roman Yeryomin
2016-05-05 15:32 ` Dave Taht
2016-05-05 16:07 ` Roman Yeryomin
2016-05-05 16:59 ` Jonathan Morton
2016-05-05 17:39 ` Roman Yeryomin
2016-05-05 18:16 ` Dave Taht
2016-05-05 18:33 ` Dave Taht
2016-05-05 16:12 ` Eric Dumazet
2016-05-05 16:25 ` Roman Yeryomin
2016-05-05 16:42 ` Roman Yeryomin
2016-05-06 10:55 ` Roman Yeryomin
2016-05-05 19:23 ` Eric Dumazet
2016-05-05 19:41 ` Dave Taht
2016-05-06 8:41 ` moeller0
2016-05-06 11:33 ` Jesper Dangaard Brouer
2016-05-06 11:46 ` moeller0
2016-05-06 13:25 ` Eric Dumazet
2016-05-06 15:25 ` moeller0
2016-05-06 15:58 ` Eric Dumazet
2016-05-06 16:30 ` moeller0
2016-05-06 15:55 ` [PATCH net-next] fq_codel: add memory limitation per queue Eric Dumazet
2016-05-09 3:49 ` David Miller
2016-05-09 4:14 ` Cong Wang
2016-05-09 4:31 ` Eric Dumazet
2016-05-09 5:07 ` Cong Wang
2016-05-09 14:26 ` Eric Dumazet
2016-05-10 4:34 ` Cong Wang
2016-05-10 4:45 ` Eric Dumazet
2016-05-10 4:57 ` Cong Wang
2016-05-10 5:10 ` Eric Dumazet
2016-05-16 1:16 ` [PATCH net-next] fq_codel: fix memory limitation drift Eric Dumazet
2016-05-17 1:57 ` David Miller
2016-05-06 9:42 ` OpenWRT wrong adjustment of fq_codel defaults (Was: fq_codel_drop vs a udp flood) Jesper Dangaard Brouer
2016-05-06 9:42 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Jesper Dangaard Brouer
2016-05-06 12:47 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Jesper Dangaard Brouer
2016-05-06 12:47 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Jesper Dangaard Brouer
2016-05-06 18:43 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Roman Yeryomin
2016-05-06 18:43 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Roman Yeryomin
2016-05-06 18:56 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Roman Yeryomin
2016-05-06 18:56 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Roman Yeryomin
2016-05-06 19:43 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Dave Taht
2016-05-06 19:43 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Dave Taht
2016-05-15 22:34 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Roman Yeryomin
2016-05-15 22:34 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Roman Yeryomin
2016-05-15 23:07 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Eric Dumazet
2016-05-15 23:07 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Eric Dumazet
2016-05-15 23:27 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Roman Yeryomin
2016-05-15 23:27 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Roman Yeryomin
2016-05-16 8:12 ` [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: " David Lang
2016-05-16 8:12 ` [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " David Lang
2016-05-16 8:26 ` Roman Yeryomin
2016-05-16 8:26 ` Roman Yeryomin
2016-05-16 8:46 ` [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: " David Lang
2016-05-16 8:46 ` [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " David Lang
2016-05-16 10:34 ` [OpenWrt-Devel] [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: " Sebastian Moeller
2016-05-16 10:34 ` [OpenWrt-Devel] [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Sebastian Moeller
2016-05-16 8:14 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Roman Yeryomin
2016-05-16 8:14 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Roman Yeryomin
2016-05-16 14:23 ` [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: " Eric Dumazet
2016-05-16 14:23 ` [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Eric Dumazet
2016-05-16 16:04 ` Dave Taht
2016-05-16 16:04 ` Dave Taht
2016-05-16 19:46 ` OpenWRT wrong adjustment of fq_codel defaults (Was: " Roman Yeryomin
2016-05-16 19:46 ` OpenWRT wrong adjustment of fq_codel defaults (Was: [Codel] " Roman Yeryomin
2016-05-07 9:57 ` Kevin Darbyshire-Bryant
2016-05-15 22:47 ` Roman Yeryomin
2016-05-15 22:47 ` Roman Yeryomin
2016-05-03 2:26 ` Dave Taht [this message]
2016-05-03 5:21 ` [Codel] fq_codel_drop vs a udp flood Dave Taht
2016-05-03 12:39 ` Agarwal, Anil
2016-05-03 12:50 ` Agarwal, Anil
2016-05-03 13:35 ` Eric Dumazet
2016-05-03 15:37 ` Agarwal, Anil
2016-05-03 17:37 ` Dave Taht
2016-05-03 17:54 ` Eric Dumazet
2016-05-03 18:11 ` Dave Taht
2016-05-03 13:20 ` Kevin Darbyshire-Bryant
2016-05-01 18:26 ` Dave Taht
2016-05-01 22:30 ` Eric Dumazet
2016-05-02 14:09 ` Roman Yeryomin
2016-05-02 15:04 ` Eric Dumazet
2016-05-02 15:42 ` Roman Yeryomin
2016-05-02 13:47 ` [Make-wifi-fast] " Roman Yeryomin
2016-05-02 15:01 ` Eric Dumazet
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