Re: [Cake] Cake3 - source code and some questions

["Toke Høiland-Jørgensen" <toke@toke.dk>]

Adrian Popescu <adriannnpopescu@gmail.com> writes:

> Seeing worse latency under load (20-100 milliseconds) isn't uncommon.
> I believe this to be a regression in the kernel or in the network
> drivers.

I don't see this behaviour at all:

$ ls -l /sys/class/net/enp0s25/device/driver                                                                                                                                                                                   :(
0 lrwxrwxrwx 1 root root 0 Apr 21 16:05 /sys/class/net/enp0s25/device/driver -> ../../../bus/pci/drivers/e1000e/

$ ping 130.243.26.1 -c 100 # this is my default gateway
..snip...
--- 130.243.26.1 ping statistics ---
100 packets transmitted, 100 received, 0% packet loss, time 99000ms
rtt min/avg/max/mdev = 0.341/0.801/28.260/2.769 ms

$ cat /proc/loadavg 
9.29 8.43 5.30 14/508 6665

(yes, this is while running a cpu-hungry data processing application in
the background on all eight cores)

$ uname -a
Linux alrua-kau 3.19.3-3-ARCH #1 SMP PREEMPT Wed Apr 8 14:10:00 CEST 2015 x86_64 GNU/Linux

$  tc qdisc show dev enp0s25
qdisc pfifo_fast 0: root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1

(hmm, why am I running pfifo_fast?)

Repeating with sch_fq:

$ ping 130.243.26.1 -c 100
...snip...
--- 130.243.26.1 ping statistics ---
100 packets transmitted, 100 received, 0% packet loss, time 98998ms
rtt min/avg/max/mdev = 0.358/0.468/1.278/0.151 ms

-Toke