Gromacs free energy computation

hi dear investigators. during free energy calculation by gromacs, I cant use from all the power of GPU and only 2% of its power is used. The use of the -nb GPU and -pme gpu did not change either.

How big is the system (number of atoms)? If it’s small, you may not get full utilization of the GPU.

Note that using all GPU power is not related to the number of atoms, because in normal simulation for my system, all GPU power is used. my peptide have 33 residues.