1080Ti gots slower after reinstalling ubuntu

After I reinstalled my ubuntu on PC, I installed all libs and drivers and then run caffe time with the same model, to test the forward pass time.

Originally ,before I resintall my OS, the forward time is 6 ms , but now it becomes 8 ms at the first time after I reinstall the driver , and after the first run, the forward time becomes 17 ms , then it stays 17ms . It’s much slower.

How is that ?

My os is Ubuntu 16.04, GPU is 1080Ti, Driver is NVIDIA-Linux-x86_64-410.73.run.
cuda :cuda_9.0.176_384.81_linux.run.

The caffe config file is totally the same with the old version on which the forward time is 6 ms.

Hoping for your reply!