Originally Posted by simplex5
say a process is executing and i just see that its priority should be changed then what is the way to change its nice value to do the same
It sort of depends on your distribution.
The renice command can change the listed priority.
But if your system is using cgroups (control groups - for controlling multiple processes as a unit), it will have little to no effect. Nice values are only used inside a cgroup, and the scheduling of cgroups (which is a global scheduling) overrides the nice values. The end result is that processes within a cgroup (as controlled by the nice value) only order the processes within that cgroup. It doesn't have any effect on processes in other cgroups.