I have made some instructions and even some ready made builds which include the hrtimer patch which should mitigate the severe performance degradation of IPQ806x
Severe performance degradation for IPQ806x Kernel 5.11 and higher.
Recently a bug has been discovered which explains the severe performance
degradation for IPQ806x Kernel 5.11 and higher:
https://github.com/openwrt/openwrt/issues/11676
https://github.com/openwrt/openwrt/pull/13323
https://www.spinics.net/lists/netdev/msg931629.html
In short the introduction of hrtimer in
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c and drivers/net/ethernet/stmicro/stmmac/stmmac.h seems to have introduced a bug for the krait cores which started wasting many CPU cycles re-arming the hrtimer.
See commit:
https://github.com/torvalds/linux/commit/d5a05e69ac6e4c431c380ced2b534c91f7bc3280
The included patch reverts this commit.
This patch is a workaround as there could be unwanted side effects but the devs are studying on a proper solution, but in the mean time you can try this.
From the Github repo: https://github.com/egc112/OpenWRT-egc-add-on download the zip file (under the green <> Code button)
Extract the content of the patches directory in the zip file to your patches directory.
There are two hrtimer patches, one for Kernel 5.15 (23.05) in /patches/root/5.15 and for Kernel 6.1 (Main/Master) in /patches/root/6.1.
After you have prepared your build system and are ready to compile, copy the patch for the Kernel version you are using to the OpenWRT root directory.
From that directory execute the patch (this is for Kernel 5.15) with:
patch -p1 < 901-net-stmmac-revert-hrtimer-5.15.patch
This patch will add the following file to target/linux/ipq806x/patches-5.15/901-net-stmmac-revert-hrtimer.patch
You can simply check with:
ls target/linux/ipq806x/patches-5.15/901-net-stmmac-revert-hrtimer.patch
Alternatively there is a ready made build with this hrtimer patch for Linksys EA8500 and Netgear R7800.
Both 23.05 Snapshot, basic builds with wireless, Luci, WireGuard and OpenVPN.
Both tested on my own routers and both are working FWIW 