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    [...]
    The advantage is that for example to read a local percpu variable,
    instead of this sequence:
    
     return __get_cpu_var(var);
    
     ffffffff8102ca2b:  48 8b 14 fd 80 09 74    mov    -0x7e8bf680(,%rdi,8),%rdx
     ffffffff8102ca32:  81
     ffffffff8102ca33:  48 c7 c0 d8 59 00 00    mov    $0x59d8,%rax
     ffffffff8102ca3a:  48 8b 04 10             mov    (%rax,%rdx,1),%rax
    
    We can get a single instruction by using the optimized variants:
    
     return percpu_read(var);
    
     ffffffff8102ca3f:  65 48 8b 05 91 8f fd    mov    %gs:0x7efd8f91(%rip),%rax
    [...]

So if you want to make use of it, percpu_add()/percpu_sub() would be 
the place to start.

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