New result with latest ayufan image where he switched to CONFIG_HZ=250 but still at 1.8/1.4GHz:
Memory performance (big.LITTLE cores measured individually):
memcpy: 1800.4 MB/s
memset: 8313.6 MB/s
memcpy: 3513.9 MB/s
memset: 8410.0 MB/s (0.5%)
Vs. Edge/Captain also with CONFIG_HZ=250 but at 2.0/1.5GHz:
Memory performance (big.LITTLE cores measured individually):
memcpy: 1391.1 MB/s (0.2%)
memset: 4821.1 MB/s
memcpy: 2856.5 MB/s (0.3%)
memset: 4882.2 MB/s (0.6%)
Significant change was this and afterwards memory performance was reported at same level as mainline kernel.
Maybe CONFIG_ARM_ROCKCHIP_DMC_DEVFREQ is the culprit? linux-kernel/arch/arm64/configs/rockchip_linux_defconfig at ed3ce4d15ec1c8721b55fbc6860b44907ea9eba5 · ayufan-rock64/linux-kernel · GitHub vs. https://github.com/armbian/build/blob/master/config/kernel/linux-rk3399-default.config#L5174-L5179
Interestingly on ayufan’s image /sys/bus/platform/drivers/rockchip-dmc/dmc/ is missing completely…