Can't torch multiprocessing pass model parameters correctly?

In order to improve the utilization of the graphics card, I decided to run multiple models at the same time. I find that torch.multiprocessing could finish it.
Here is my code.

import torch.multiprocessing as mp
pool = []
for i in range(num_workers):
model = torch.load(…).eval()
p = mp.Process(
target=target_function,
args=(arg1, arg2, model)
)
p.start()
pool.append(p)
for p in pool:
p.join()
However, all the params of model in target_function is 0. I guess there is some problem in passing the model parameters. So how to slove this problem.