[Cake] small cake_hash optimization?

[Sebastian Moeller]

Hi Pete,

> On Nov 22, 2017, at 19:43, Pete Heist <peteheist at gmail.com> wrote:
> 
> 
>> On Nov 22, 2017, at 7:33 PM, Dave Taht <dave.taht at gmail.com> wrote:
>> 
>> On Wed, Nov 22, 2017 at 4:37 AM, Pete Heist <peteheist at gmail.com> wrote:
>>> 
>>> Ok, at least a little crude testing with sar:
>>> 
>>> https://docs.google.com/spreadsheets/d/1LKoq5NaswuHm9H1atXoZA1AhNDg6L4UYS3Pn5lCsb1I/edit#gid=0
>>> 
>>> ~10% less cake CPU at GigE in this case?
>> 
>> Divides do hurt, particularly if you can't do them out of order. But
>> that seems like a lot.
> 
> Hrm, I tried a second test to make sure fairness still works (it does) but this time got a slight _negative_ result (rrul_be fair tab). So this calls into question whether or not my testing method is very good, and also whether or not the change actually helps much.
> 
> This time I used "cake unlimited besteffort dual-srchost overhead 64 mpu 84” (overheads from Sebastian, just rely on bql).

	I should have mentioned "overhead 64 mpu 84" only make sense in combination with a shaper limit (well, they will make sure the cake statistics will be more reflective of what is happening on the ethernet wire, but I am not sure whether that is worth the run-time cost the overhead calculation incurs).

Somewhat unrelated, I wondered about all the excitement about irtt and cloned the repository to my mac, and was absolutely delighted to realize that irtt will also effortlessly work under macos. I only have run the demo from the readme.md with both client and server running at the same machine, but I got results that look reasonable on first sight (but I admit I really do not know exact;y what to expect). This is really great!


Best Regards


> 
> I might try again with 950mbit limiting, and ‘perf’ instead.
> 
> Also I noted that the ‘lan’ keyword seemed to adversely affect host fairness, so I stopped using it. I’ll address that separately when there’s time.
> 
>>> What’s a better tool for timing
>>> kernel module functions?
>> 
>> Use "perf"
>> 
>> https://en.wikipedia.org/wiki/Perf_(Linux)
> 
> Ok, will see if I can give it a try.
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