The sysctl interface provides a means of dynamically changing
certain kernel parameters and variables on the fly without requiring
a recompile of the kernel or reboot of the system. The primary
interface is through /proc/sys. If you say Y here a tree of
modifiable sysctl entries will be generated beneath the
/proc/sys directory. They are explained in the files
in Documentation/sysctl/. Note that enabling this
option will enlarge the kernel by at least 8 KB.

As it is generally a good thing, you should say Y here unless
building a kernel for install/rescue disks or your system is very
limited in memory.