Well, on real big.LITTLE designs there is one cluster of fast CPU cores (A15, A17, A72, A73, …) combined with one cluster of slow but energy efficient cores (A7, A53). On the S912 there’s just 8 slow cores made in the same process (no idea whether it’s 28nm or 40nm – I don’t trust in a single word told by Amlogic any more). So there is simply no reason to limit one cluster to 1 GHz and allow the other to operate at 1.4 GHz.
Other SoC designs with similar little.LITTLE implementation (Allwinner A83T with 8xA7 or Samsung/Nexell S5P6818 with 8xA53) of course allow to clock all CPU cores identically. On those designs there’s also no scheduler problem like with S912 now where the scheduler puts demanding tasks on the slower slow cores instead of the 1.4 GHz cluster.
Since someone said the cluster would show different consumption behaviour… why? It’s the same cores just with different artificial clockspeed limits. By locking the ‘fast’ cluster to 1 GHz and using taskset with any demanding load it should be easy to check for this. But I really doubt that there are consumption differences.
And if consumption would be an issue then the user should be able to control cpufreq behaviour on his own. But not even this is possible as we’ve seen since without fixed CPU affinitiy the bl30.bin BLOB uses whatever cpufreq OPPs below 1000 MHz anyway.
And then due to 4 cores being limited to just 1.0 GHz and 4 to 1.4 GHz the Vim2 should not be advertised as ‘1.5 GHz 64Bit Octa Core ARM Cortex-A53’ since in octa-core mode it’s just 1.2 GHz on average. And the available performance data doesn’t look good for the Vim2 anyway. Now that you discovered this scheduler weirdness with the 4.9 kernel with demanding tasks sent to the slowest cores at least it gets understandable.
Still interested in the results of the following two benchmarks testing for combined CPU+memory performance and only memory:
taskset -c 0-3 7zr b -mmt4
taskset -c 4-7 7zr b -mmt4
taskset -c 3 tinymembench
taskset -c 7 tinymembench
Requires an apt install p7zip and for tinymembench a quick compilation. @g4b42 already provided tinymembench numbers but as we learned recently the scheduler at least with 4.9 kernel behaves weird and demanding tasks end up on the slowest CPU cores. And at least with real big.LITTLE designs running on the two clusters results in a huge memory performance difference!