CONFIG_VDSO is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Enable VDSO for acceleration of some system calls

modulename: vdso.ko

configname: CONFIG_VDSO

Linux Kernel Configuration
└─>Enable VDSO for acceleration of some system calls
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Place in the process address space an ELF shared object
providing fast implementations of gettimeofday and
clock_gettime. Systems that implement the ARM architected
timer will receive maximum benefit.

You must have glibc 2.22 or later for programs to seamlessly
take advantage of this.

source code: