cmp(1) has a bottleneck, but where?

[Dieter BSD]

>> Task: cp(1) a several-GB file from one drive to another,
>> then run cmp(1) to verify.  Cp runs as expected, but
>> cmp runs slower than expected.  Neither the disks
>> nor the cpu is maxed out.  Local drives, no network
>> involved.  Machine is otherwise idle.
>
>    1. How are you running cmp?
>    2. Why do you claim cmp is the bottleneck? Is it spinning the CPU?

cmp big_file /other_disk/big_file

Cmp is running slower than it should.  It isn't cpu bound ( 67.5%Idle )
but it isn't disk bound either.  Seems like it should be one or the
other.