Re: [Cake] cake flenter results round 1

[Dave Taht <dave.taht@gmail.com>]

georgios

the result you got was "fair", but you shoul have seen something
closer to 900mbit than 400.

On Mon, Nov 27, 2017 at 8:17 AM, Georgios Amanakis <gamanakis@gmail.com> wrote:
> Dear Pete,
>
> I am trying to replicate the unfair behaviour you are seeing with
> dual-{src,dst}host, albeit on different hardware and I am getting a fair
> distribution. Hardware are Xeon E3-1220Lv2 (router), i3-3110M(Clients). All
> running Archlinux, latest cake and patched iproute2-4.14.1, connected with
> Gbit ethernet, TSO/GSO/GRO enabled.
>
> Qdisc setup:
> ----------------
> Router:
> qdisc cake 8003: dev ens4 root refcnt 2 bandwidth 900Mbit diffserv3
> dual-dsthost rtt 100.0ms raw
>
> Client A(kernel default):
> qdisc fq_codel 0: dev eno2 root refcnt 2 limit 10240p flows 1024 quantum
> 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn
>
> Client B (kernel default):
> qdisc fq_codel 0: dev enp1s0 root refcnt 2 limit 10240p flows 1024 quantum
> 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn
> ----------------
>
>
> Cli:
> ----------------
> Router:
> netserver &
>
> Client A:
> flent tcp_1down -H router
>
> Client B:
> flent tcp_12down -H router
> ----------------
>
>
> Results:
> ----------------
> Router:
> qdisc cake 8003: root refcnt 2 bandwidth 900Mbit diffserv3 dual-dsthost rtt
> 100.0ms raw
>  Sent 7126680117 bytes 4725904 pkt (dropped 10, overlimits 4439745 requeues
> 0)
>  backlog 0b 0p requeues 0
>  memory used: 1224872b of 15140Kb
>  capacity estimate: 900Mbit
>                  Bulk   Best Effort      Voice
>   thresh     56250Kbit     900Mbit     225Mbit
>   target         5.0ms       5.0ms       5.0ms
>   interval     100.0ms     100.0ms     100.0ms
>   pk_delay        14us       751us         7us
>   av_delay         2us       642us         1us
>   sp_delay         1us         1us         1us
>   pkts          109948     4601651       14315
>   bytes      160183242  6964893773     1618242
>   way_inds           0       21009           0
>   way_miss         160         188           5
>   way_cols           0           0           0
>   drops              0          10           0
>   marks              0           0           0
>   ack_drop           0           0           0
>   sp_flows           0           1           1
>   bk_flows           1           0           0
>   un_flows           0           0           0
>   max_len         7570       68130        1022
>
>
> Client A:
>                            avg       median          # data pts
>  Ping (ms) ICMP :         0.11         0.08 ms              350
>  TCP download   :       443.65       430.38 Mbits/s         301
>
>
> Client B:
>                              avg       median          # data pts
>  Ping (ms) ICMP   :         0.09         0.06 ms              350
>  TCP download avg :        37.03        35.87 Mbits/s         301
>  TCP download sum :       444.35       430.40 Mbits/s         301
>  TCP download::1  :        37.00        35.87 Mbits/s         301
>  TCP download::10 :        37.01        35.87 Mbits/s         301
>  TCP download::11 :        37.02        35.87 Mbits/s         301
>  TCP download::12 :        37.00        35.87 Mbits/s         301
>  TCP download::2  :        37.03        35.87 Mbits/s         301
>  TCP download::3  :        36.99        35.87 Mbits/s         301
>  TCP download::4  :        37.03        35.87 Mbits/s         301
>  TCP download::5  :        37.07        35.87 Mbits/s         301
>  TCP download::6  :        37.00        35.87 Mbits/s         301
>  TCP download::7  :        37.12        35.87 Mbits/s         301
>  TCP download::8  :        37.05        35.87 Mbits/s         301
>  TCP download::9  :        37.03        35.87 Mbits/s         301
> ----------------
>
> Does this suggest that it is indeed a problem of an underpowered CPU in your
> case?
>
> George
>
>
> On Mon, Nov 27, 2017 at 10:53 AM, Pete Heist <peteheist@gmail.com> wrote:
>>
>>
>> On Nov 27, 2017, at 3:48 PM, Jonathan Morton <chromatix99@gmail.com>
>> wrote:
>>
>> It's not at all obvious how we'd detect that.  Packets are staying in the
>> queue for less time than the codel target, which is exactly what you'd get
>> if you weren't saturated at all.
>>
>> That makes complete sense when you put it that way. Cake has no way of
>> knowing why the input rate is lower than expected, even if it’s part of the
>> cause.
>>
>> I don’t think flent can know this either. It can’t easily know the cause
>> for its total output to be lower than expected.
>>
>> All I know is, this is a common problem in deployments, particularly on
>> low-end hardware like ER-Xs, that can be tricky for users to figure out.
>>
>> I don’t even think monitoring CPU in general would work. The CPU could be
>> high because it’s doing other calculations, but there’s still enough for
>> cake at a low rate, and there’s no need to warn in that case. I’d be
>> interested in any ideas on how to know this is happening in the system as a
>> whole. So far, there are just various clues that one needs to piece together
>> (no or few drops or marks, less total throughput that expected, high cpu
>> without other external usage, etc). Then it needs to be proven with a test.
>>
>> Anyway thanks, your clue was what I needed! I need to remember to review
>> the qdisc stats when something unexpected happens.
>>
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>>
>
>
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>



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Dave Täht
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