The device DT contains capacity-dmips-mhz = <530>; for the A55 and capacity-dmips-mhz = <1024>; for the A76 as such the scheduler should prefer the latter for jobs. Works just fine for me (using ondemand for reasons):
tk@rock-5b:~$ 7zr b -mmt=1
7-Zip (a) [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=eo_US.UTF-8,Utf16=on,HugeFiles=on,64 bits,8 CPUs LE)
LE
CPU Freq: - - - 64000000 - - - - -
RAM size: 15720 MB, # CPU hardware threads: 8
RAM usage: 435 MB, # Benchmark threads: 1
Compressing | Decompressing
Dict Speed Usage R/U Rating | Speed Usage R/U Rating
KiB/s % MIPS MIPS | KiB/s % MIPS MIPS
22: 2196 100 2140 2137 | 37441 100 3198 3197
23: 2001 100 2044 2039 | 36239 100 3139 3137
24: 1918 100 2066 2063 | 34390 100 3020 3019
25: 1823 100 2084 2082 | 32139 100 2862 2861
---------------------------------- | ------------------------------
Avr: 100 2083 2080 | 100 3055 3053
Tot: 100 2569 2567
tk@rock-5b:~$ taskset -c 7 7zr b -mmt=1
7-Zip (a) [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=eo_US.UTF-8,Utf16=on,HugeFiles=on,64 bits,8 CPUs LE)
LE
CPU Freq: 64000000 - - - - 256000000 - - -
RAM size: 15720 MB, # CPU hardware threads: 8
RAM usage: 435 MB, # Benchmark threads: 1
Compressing | Decompressing
Dict Speed Usage R/U Rating | Speed Usage R/U Rating
KiB/s % MIPS MIPS | KiB/s % MIPS MIPS
22: 2164 100 2108 2106 | 37132 100 3172 3170
23: 1992 100 2033 2030 | 36189 100 3134 3133
24: 1908 100 2054 2052 | 34312 100 3013 3012
25: 1822 100 2083 2081 | 31840 100 2835 2834
---------------------------------- | ------------------------------
Avr: 100 2070 2067 | 100 3038 3037
Tot: 100 2554 2552
Wrt IRQ affinity I would believe the best is static mappings suitable for different use cases (moving e.g. PCIe and USB3 interrupts away from cpu0 to another little core).