That’s really strange since when I tested with CONFIG_HZ=1000 I got similar results wrt memory performance: sbc-bench/Results.md at master · ThomasKaiser/sbc-bench · GitHub
According to ayufan the way lower memory performance with Rockchip’s BSP kernel compared to mainline is related to CONFIG_HZ and switching from 1000 to 250 fixed it for him. Hmm… I need to test with my RockPro64 tomorrow…
So the result in https://github.com/ThomasKaiser/sbc-bench/blob/master/Results.md for RockPro64 4.4 kernel is CONFIG_HZ=250 ? I found the memory performance is lower then mainline kernel.
Nope, that was also with CONFIG_HZ=1000 – I need to retest soon.
Now that @balbes150 pushed his Armbian changes (using 250Hz and the other tweaks already) I’ll test with his images. 
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…