GPU Utilization in Gromacs2021.3 is low, about 80%

GROMACS version:2021.3


CPU: Intel(R) Xeon(R) Platinum 8273CL CPU @ 2.20GHz 28cores

GROMACS modification: No

when I submit the first task, the GPU usage is 52%.
but I submit the secont task on the same GPU, the GPU usage is 80%.
I think that the GPU usage should be about 100%. This result make me confused.
Is this normal? I want to know.

I used 9 cores for every task.
my gmx command:

# first task
gmx mdrun -v -deffnm ./md/md -pin on -ntmpi 1 -ntomp 9 -pme gpu -nb gpu -gpu_id 1 -pinoffset 0

# sencond task
gmx mdrun -v -deffnm ./md/md -pin on -ntmpi 1 -ntomp 9 -pme gpu -nb gpu -gpu_id 1 -pinoffset 18

When I submit second task on another GPU, now two GPUs is about 40 %.

When second task is over,
I guess it’s the heat dissipation of the server computer.

Wich card is this and what simulations are you running?
This is expected; performance or usage doest added up in linear.

ok, thanks

Try using the GPU-resident mode with -update gpu. If your simulation settings are compatible, this should trade CPU idling for keeping the GPU busy (and moving data between CPU-GPU less frequently if possible).