[Cake] net-next is open

[Cake] net-next is open

[Dave Taht]

http://vger.kernel.org/~davem/net-next.html

Can I garner a few Signed-off-by's?

I will add tested-by for georgio and pete.

-- 

Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619

Re: [Cake] net-next is OPEN...

[Toke Høiland-Jørgensen]

Pete Heist <pete@eventide.io> writes:

>> On Apr 18, 2018, at 7:43 AM, Pete Heist <pete@eventide.io> wrote:
>> 
>> I also think I saw this happen at lower bandwidths as well, when the CPU wasn’t loaded. What I’ll do is re-test on the current version I have at, say, 50Mbit (or to where load drops substantially), then update to the head and test again, and let you know...
>> 
>>> On Apr 17, 2018, at 3:52 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
>>> 
>>>> On 16 Apr, 2018, at 11:55 pm, Pete Heist <pete@eventide.io> wrote:
>>>> 
>>>> I remember that fairness behavior at low RTTs (< 20ms) needed to be either improved or documented
>>> 
>>> The reason for the behaviour, IIRC, was that throughput dropped below 100% when the latency target was reduced too much.  Since then there has been a small change which might improve it a little, so a retest would be reasonable.
>
> At 50mbit I don’t see nearly as much fairness degradation at low RTTs, although there’s some. Even at 100us, “fairness” is around 1.1 (1.0 being perfectly fair) instead of the 2.x I saw at 500mbit. I do not see much of a difference between the latest code (16d7fed, 2018-04-17) and the previous code I tested (7061401, 2017-12-01), if that info is of use.
>
> RTT: tcp_1up upload Mbps / tcp_12up upload Mbps
>
> 7061401 (2017-12-01):
>
>    100us: 23.80 / 25.85
>    1ms: 23.89 / 29.46
>    10ms: 23.93 / 24.66
>    40ms: 23.96 / 24.10
>    100ms: 23.97 / 24.12
>
> 16d7fed (2018-04-17):
>
>    100us: 23.97 / 26.49
>    1ms: 23.89 / 26.27
>    10ms: 23.98 / 26.37
>    40ms: 23.94 / 24.08
>    100ms: 23.97 / 24.12
>
> I can post reports / flent files on request.
>
> So it appears this is CPU related, and not worth exploring further(?)
> and not worth documenting(?) other than that once things have
> stabilized, documenting how Cake degrades under various extreme
> conditions would be informative.

Awesome, thanks for re-testing! :)

-Toke

Re: [Cake] net-next is OPEN...

[Pete Heist]

> On Apr 18, 2018, at 7:43 AM, Pete Heist <pete@eventide.io> wrote:
> 
> I also think I saw this happen at lower bandwidths as well, when the CPU wasn’t loaded. What I’ll do is re-test on the current version I have at, say, 50Mbit (or to where load drops substantially), then update to the head and test again, and let you know...
> 
>> On Apr 17, 2018, at 3:52 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
>> 
>>> On 16 Apr, 2018, at 11:55 pm, Pete Heist <pete@eventide.io> wrote:
>>> 
>>> I remember that fairness behavior at low RTTs (< 20ms) needed to be either improved or documented
>> 
>> The reason for the behaviour, IIRC, was that throughput dropped below 100% when the latency target was reduced too much.  Since then there has been a small change which might improve it a little, so a retest would be reasonable.

At 50mbit I don’t see nearly as much fairness degradation at low RTTs, although there’s some. Even at 100us, “fairness” is around 1.1 (1.0 being perfectly fair) instead of the 2.x I saw at 500mbit. I do not see much of a difference between the latest code (16d7fed, 2018-04-17) and the previous code I tested (7061401, 2017-12-01), if that info is of use.

RTT: tcp_1up upload Mbps / tcp_12up upload Mbps

7061401 (2017-12-01):

   100us: 23.80 / 25.85
   1ms: 23.89 / 29.46
   10ms: 23.93 / 24.66
   40ms: 23.96 / 24.10
   100ms: 23.97 / 24.12

16d7fed (2018-04-17):

   100us: 23.97 / 26.49
   1ms: 23.89 / 26.27
   10ms: 23.98 / 26.37
   40ms: 23.94 / 24.08
   100ms: 23.97 / 24.12

I can post reports / flent files on request.

So it appears this is CPU related, and not worth exploring further(?) and not worth documenting(?) other than that once things have stabilized, documenting how Cake degrades under various extreme conditions would be informative.

Well, here’s to science and a good walk in the weeds…

Re: [Cake] net-next is OPEN...

[Pete Heist]

I also think I saw this happen at lower bandwidths as well, when the CPU wasn’t loaded. What I’ll do is re-test on the current version I have at, say, 50Mbit (or to where load drops substantially), then update to the head and test again, and let you know...

Pete

> On Apr 17, 2018, at 3:52 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
> 
>> On 16 Apr, 2018, at 11:55 pm, Pete Heist <pete@eventide.io> wrote:
>> 
>> I remember that fairness behavior at low RTTs (< 20ms) needed to be either improved or documented
> 
> The reason for the behaviour, IIRC, was that throughput dropped below 100% when the latency target was reduced too much.  Since then there has been a small change which might improve it a little, so a retest would be reasonable.
> 
> - Jonathan Morton
> 

Re: [Cake] net-next is OPEN...

[Jonathan Morton]

> On 16 Apr, 2018, at 11:55 pm, Pete Heist <pete@eventide.io> wrote:
> 
> I remember that fairness behavior at low RTTs (< 20ms) needed to be either improved or documented

The reason for the behaviour, IIRC, was that throughput dropped below 100% when the latency target was reduced too much.  Since then there has been a small change which might improve it a little, so a retest would be reasonable.

 - Jonathan Morton

Re: [Cake] net-next is OPEN...

[Toke Høiland-Jørgensen]

Pete Heist <pete@eventide.io> writes:

>> On Apr 16, 2018, at 5:12 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
>> 
>> Dave Taht <dave.taht@gmail.com> writes:
>> 
>>> do we consider cake ready this time?
>> 
>> I'm not aware of anything outstanding, at least...
>
> Do I have the release cycle right that it would have to be upstreamed
> by “about 10 weeks” from now and would end up in 4.18
> (https://www.kernel.org/doc/Documentation/networking/netdev-FAQ.txt)?

Assuming it is accepted, yes... :)

> I remember that fairness behavior at low RTTs (< 20ms) needed to be
> either improved or documented, and don’t see anything about that in
> the man page in the tc-adv repo thus far. Summarizing the host
> isolation results at
> http://www.drhleny.cz/bufferbloat/cake/round2/#hostiso_cake_{rtt}_{qos-id}
> <http://www.drhleny.cz/bufferbloat/cake/round2/#hostiso_cake_%7Brtt%7D_%7Bqos-id%7D>:
>
> RTT: fairness (1.0 == perfect fairness)
> ---
> 100us: 2.22
> 1ms: 1.7
> 2ms: 1.6
> 3ms: 1.42
> 5ms: 1.31
> 8ms: 1.16
> 10ms: 1.12
> 20ms: 1.02
> 40ms: 1.017

Erm, what's the metric and which data source are you looking at here?

-Toke

Re: [Cake] net-next is OPEN...

[Pete Heist]

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> On Apr 16, 2018, at 5:12 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> 
> Dave Taht <dave.taht@gmail.com> writes:
> 
>> do we consider cake ready this time?
> 
> I'm not aware of anything outstanding, at least...

Do I have the release cycle right that it would have to be upstreamed by “about 10 weeks” from now and would end up in 4.18 (https://www.kernel.org/doc/Documentation/networking/netdev-FAQ.txt)?

I remember that fairness behavior at low RTTs (< 20ms) needed to be either improved or documented, and don’t see anything about that in the man page in the tc-adv repo thus far. Summarizing the host isolation results at http://www.drhleny.cz/bufferbloat/cake/round2/#hostiso_cake_{rtt}_{qos-id} <http://www.drhleny.cz/bufferbloat/cake/round2/#hostiso_cake_%7Brtt%7D_%7Bqos-id%7D>:

RTT: fairness (1.0 == perfect fairness)
---
100us: 2.22
1ms: 1.7
2ms: 1.6
3ms: 1.42
5ms: 1.31
8ms: 1.16
10ms: 1.12
20ms: 1.02
40ms: 1.017




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