Hi, lartc gurus
I have a home router, and want to use HTB to limit the upload speed of a user.
I connect my phone to router via wifi, got an ip 192.168.10.28 via DHCP
I limit the upload speed to 500KB/s, here is my config
# tc qdisc show dev eth0.4
qdisc htb 1: root refcnt 2 r2q 10 default 0 direct_packets_stat 18 direct_qlen 1000
qdisc pfifo 11d: parent 1:1d limit 1000p
# tc class show dev eth0.4
class htb 1:1d root leaf 11d: prio rate 4Mbit ceil 4Mbit burst 4800b cburst 4800b
# tc filter show dev eth0.4
filter parent 1: protocol ip pref 1 flow
filter parent 1: protocol ip pref 1 flow handle 0x1 map keys nfct-src and 0x000000ff baseclass 1:1
I test upload speed of phone using app, e.g. speedtest5g, or other similar app, the result double the limit.
if I change the leaf qdisc to fq_codel, then the limit is quite accurate.
# tc qdisc del dev eth0.4 handle 11d: parent 1:1d pfifo
# tc qdisc add dev eth0.4 handle 11d: parent 1:1d fq_codel
after read lots of documents and source code, I guess the reason:
qdisc has no traffic shaping when enqueue. so when the queue is empty,
packets can enqueue without limit, so there's a burst speed, while speed test app often use the max speed as result.
if i change the leaf pfifo limit from 1000p to 200p, then the test result is more closing to rate limit, but still bigger than it.
But why fq_codel is accurate?
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