• chengcui
• testD49540_reload

test patch D49540

patch link: D49540

• table of bottleneck queue size ratio to the bandwidth delay product (BDP)

VM environment with a 1GE switch

single path testbed

Virtual machines (VMs) as TCP traffic senders using iperf3 are hosted by Bhyve in a physical box (Beelink SER5 AMD Mini PC). This box uses FreeBSD 14.2 release. Another box uses VMs as traffic receivers. The two boxes are connected through a 5-Port Gigabit Ethernet Switch (TP-Link TL-SG105). The switch has a shared 1Mb (125KB) Packet Buffer Memory, which means the link buffer is at most 2.4%BDP.

testbed:

functionality show case

This test will show a general TCP congestion control window (cwnd) growth pattern before/after the patch. And also compare with the cwnd growth pattern from the Linux kernel.

• additional 40ms latency is added/emulated in the Ubuntu VM receiver with traffic shaping.
• The minimum bandwidth delay product (BDP) is 1000Mbps x 40ms == 5 Mbytes. So I configured sender/receiver with 6MB buffer(120%BDP).

root@n3ubuntu24:~ # tc qdisc add dev enp0s5 root netem delay 40ms
root@n3ubuntu24:~ # tc qdisc show dev enp0s5
qdisc netem 8001: root refcnt 2 limit 1000 delay 40ms
root@n3ubuntu24:~ #

root@n1fbsd:~ # ping -c 4 -S n1fbsd n3ubuntu24
PING n3ubuntu24 (192.168.50.32) from n1fbsdvm: 56 data bytes
64 bytes from 192.168.50.32: icmp_seq=0 ttl=64 time=43.908 ms
64 bytes from 192.168.50.32: icmp_seq=1 ttl=64 time=44.173 ms
64 bytes from 192.168.50.32: icmp_seq=2 ttl=64 time=44.258 ms
64 bytes from 192.168.50.32: icmp_seq=3 ttl=64 time=44.421 ms

--- n3ubuntu24 ping statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 43.908/44.190/44.421/0.186 ms
root@n1fbsd:~ # 

root@n1fbsd:~ # sysctl -f /etc/sysctl.conf
net.inet.tcp.hostcache.enable: 0 -> 0
kern.ipc.maxsockbuf: 10485760 -> 10485760
net.inet.tcp.sendbuf_max: 6291456 -> 6291456
net.inet.tcp.recvbuf_max: 6291456 -> 6291456
root@n1fbsd:~ #

root@n3ubuntu24:~ # sysctl -p
net.core.rmem_max = 10485760
net.core.wmem_max = 10485760
net.ipv4.tcp_rmem = 4096 131072 6291456
net.ipv4.tcp_wmem = 4096 16384  6291456
net.ipv4.tcp_no_metrics_save = 1
root@n3ubuntu24:~ #

• info for switching to the FreeBSD RACK TCP stack

root@n1fbsd:~ # kldstat
Id Refs Address                Size Name
 1    5 0xffffffff80200000  1f75ca0 kernel
 2    1 0xffffffff82810000    368d8 tcp_rack.ko
 3    1 0xffffffff82847000     f0f0 tcphpts.ko
root@n1fbsd:~ # sysctl net.inet.tcp.functions_default=rack
net.inet.tcp.functions_default: freebsd -> rack
root@n1fbsd:~ #