[Bug 300591] Wireguard + Ethernet -> Higher CPU Load
Date: Sat, 07 Nov 2026 20:57:25 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=300591
Bug ID: 300591
Summary: Wireguard + Ethernet -> Higher CPU Load
Product: Base System
Version: 15.1-STABLE
Hardware: amd64
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: kern
Assignee: bugs@FreeBSD.org
Reporter: tivolo@posteo.net
I observe a constantly higher cpu load (20%) on both of my devices using
wireguard *and* an ethernet interface. Disabling wireguard results in a normal
cpu load again. Using wireguard and a wlan interface results in normal cpu
load. Pf is disabled.
The issue also involves a flattering of UP and DOWN of the ethernet interface,
which can be seen in `dmesg`:
..
ue0: link state changed to UP
ue0: link state changed to DOWN
ue0: 2 link states coalesced
ue0: link state changed to DOWN
ue0: 4 link states coalesced
..
or in `route -n monitor` (see time):
..
21:00:21.101 PID 69562 add/repl iface iface#5 ue0 admin UP oper UP mtu 1500
21:00:21.103 PID 69562 add/repl iface iface#5 ue0 admin UP oper UP mtu 1500
21:00:21.105 PID 69562 add/repl iface iface#5 ue0 admin UP oper DOWN mtu 1500
21:00:21.109 PID 69562 add/repl iface iface#5 ue0 admin UP oper UP mtu 1500
21:00:21.111 PID 69562 add/repl iface iface#5 ue0 admin UP oper DOWN mtu 1500
21:00:21.113 PID 69562 add/repl iface iface#5 ue0 admin UP oper DOWN mtu 1500
21:00:21.117 PID 69562 add/repl iface iface#5 ue0 admin UP oper UP mtu 1500
21:00:21.120 PID 69562 add/repl iface iface#5 ue0 admin UP oper UP mtu 1500
21:00:21.126 PID 69562 add/repl iface iface#5 ue0 admin UP oper DOWN mtu 1500
..
Disabling wireguard `service wireguard stop` also stabilizes the ethernet
interface resp. no flattering anymore.
Here are some more information about the cpu load from `top`:
```
last pid: 97547; load averages: 1,83, 2,03, 1,96; battery: 97%
up 0+03:30:32 18:25:22
989 threads: 9 running, 952 sleeping, 28 waiting
CPU 0: 9,1% user, 0,0% nice, 21,4% system, 0,6% interrupt, 68,9% idle
CPU 1: 11,0% user, 0,0% nice, 23,0% system, 0,9% interrupt, 65,1% idle
CPU 2: 15,4% user, 0,0% nice, 20,4% system, 0,3% interrupt, 63,8% idle
CPU 3: 12,9% user, 0,0% nice, 18,2% system, 2,5% interrupt, 66,4% idle
CPU 4: 10,7% user, 0,0% nice, 20,1% system, 1,6% interrupt, 67,6% idle
CPU 5: 10,4% user, 0,0% nice, 23,3% system, 0,6% interrupt, 65,7% idle
Mem: 758M Active, 1414M Inact, 17M Laundry, 2372M Wired, 76K Buf, 2782M Free
ARC: 1340M Total, 712M MFU, 582M MRU, 666K Anon, 7243K Header, 27M Other
1187M Compressed, 2397M Uncompressed, 2,02:1 Ratio
PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND
11 root 199 ki31 0B 96K CPU4 4 145:28 67,21% [idle{idle:
cpu4}]
11 root 199 ki31 0B 96K RUN 5 145:10 66,54% [idle{idle:
cpu5}]
11 root 199 ki31 0B 96K CPU3 3 147:10 66,36% [idle{idle:
cpu3}]
11 root 199 ki31 0B 96K CPU0 0 144:43 66,16% [idle{idle:
cpu0}]
11 root 199 ki31 0B 96K RUN 1 144:11 65,86% [idle{idle:
cpu1}]
11 root 199 ki31 0B 96K RUN 2 143:52 64,61% [idle{idle:
cpu2}]
43518 root 95 0 16M 4792K CPU4 4 2:57 19,32%
/usr/local/bin/bash /usr/local/bin/wg-quick up vpn-de-223
6318 user 1 0 106M 50M select 5 0:17 5,45%
/usr/local/bin/xfce4-terminal{xfce4-terminal}
8864 _dhcp 1 0 14M 3084K select 1 5:04 2,60% dhclient:
ue0 (dhclient)
```
I am using FreeBSD 15.1-RELEASE-p5 on all of my devices.
Device A is using an usb ethernet, device B is using a physical ethernet
interface.
Some similar issue is also observed by others, also in combination with
wireguard:
https://forums.freebsd.org/threads/internet-connection-going-up-and-down-constantly.95078/
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