To identify the minimum or maximum of two values often a simple if else construct is used:

if (a < b) min = a; else min = b;

or more compact using the ternary operator:

min = (a < b) ? a : b;

The generated instructions for the first if/else construct and the ternary operator does not differs. At least if the compiler is instructed to optimize the code. If the code is not optimized the compiler generates a little bit awkward code with a branch for the former example. The later use a branch free cmovle instruction on a x86_64 architecture:

[...]
movl  %edi, -20(%rbp)
movl  %esi, -24(%rbp)
movl  -20(%rbp), %eax
cmpl  %eax, -24(%rbp)
cmovle  -24(%rbp), %eax
movl  %eax, -4(%rbp)
movl  -4(%rbp), %eax
leave

The kernel provided macros for min/max extend this by execute an apparently unnecessary pointer comparison via:

(void) (&_max1 == &_max2);

This check was introduced to enable strict type-checking to make sure that both arguments are of the same type. I build a patch to extend the current two operand limited macro and enable the use for three operands too. This will save some bytes on the stack as well as some processing cycles:

#define min3(x, y, z) ({            \
    typeof(x) _min1 = (x);          \
    typeof(y) _min2 = (y);          \
    typeof(z) _min3 = (z);          \
    (void) (&_min1  &_min2  &_min3);    \
    _min1 < _min2 ? (_min1 < _min3 ? _min1 : _min3) : \
         (_min2 < _min3 ? _min2 : _min3); })