This patchset adds BPF_MAP_TYPE_PERCPU_HASH map type which allows
percpu value.
BPF + kprobe is very useful in statistics collection. In particular,
bpf is strong in doing aggregation within the kernel instead of
outputting a lot of raw samples to the userspace.
In some cases, bumping a counter/value of a particular key will have
noticeable impact. For example, doing statistics collection
on received packets and aggregating them by network
prefix (like /64 in IPv6). Having a percpu value can help.