vdso - Optimize system call performance

Use the vdso= kernel parameter to control the vdso support for the gettimeofday, clock_getres, and clock_gettime system calls.

The virtual dynamic shared object (vdso) support is a shared library that the kernel maps to all dynamically linked programs. The glibc detects the presence of the vdso and uses the functions that are provided in the library.

Because the vdso library is mapped to all user-space processes, this change is visible in user space. In the unlikely event that a user-space program does not work with the vdso support, you can disable the support.

The default, which is to use vdso support, works well for most installations. Do not override this default, unless you observe problems.

The vdso support is included in the Linux kernel.

1! vdso=
2.1 1
2.1 on
1? vdso=
2.1 0
2.1 off

      vdso=0