The sources of the stutters I can come up with are:
1. all available LITTLE cores are busy and at least a task wake up in the meantime. 2. the CPU scheduler doesn't schedule properly (from the user experience perspective). 3. music player doesn't advice itself as latency-sensitive app.
It's easy for modern smartphones to have ready_to_run_tasks (daemons) > available_cpus, and a CPU scheduler which ignores latency-sensitive apps can easily preempt the music player.
To sum up, user experience is probably the utmost thing that modern phones care, how can things like "stutters during music playing" happen? Can't we just defer those daemon tasks?
(maybe this is why my collegue got a MP3 player instead)