I’ve tried another spec Intel machine as follows:
HW SPEC
     cpu : Intel(R) Xeon(R) silver 4110 cpu @ 2.10GHz (skylake) 
mem size : 65673788 kB
     gpu : Geforce GTX 1080ti x4

touch.__config__.parallel_info()
1.8.0.dev20201014+cu101
ATen/Parallel:
        at::get_num_threads() : 1
        at::get_num_interop_threads() : 8
OpenMP 201511 (a.k.a. OpenMP 4.5)
        omp_get_max_threads() : 1
Intel(R) Math Kernel Library Version 2020.0.0 Product Build 20191122 for Intel(R) 64 architecture applications
        mkl_get_max_threads() : 1
Intel(R) MKL-DNN v1.6.0 (Git Hash 5ef631a030a6f73131c77892041042805a06064f)
std::thread::hardware_concurrency() : 16
Environment variables:
        OMP_NUM_THREADS : [not set]
        MKL_NUM_THREADS : [not set]
ATen parallel backend: OpenMP


touch.__config__.show()
PyTorch built with:
  - GCC 7.3
  - C++ Version: 201402
  - Intel(R) Math Kernel Library Version 2020.0.0 Product Build 20191122 for Intel(R) 64 architecture applications
  - Intel(R) MKL-DNN v1.6.0 (Git Hash 5ef631a030a6f73131c77892041042805a06064f)
  - OpenMP 201511 (a.k.a. OpenMP 4.5)
  - NNPACK is enabled
  - CPU capability usage: AVX2
  - CUDA Runtime 10.1
  - NVCC architecture flags: -gencode;arch=compute_37,code=sm_37;-gencode;arch=compute_50,code=sm_50;-gencode;arch=compute_60,code=sm_60;-gencode;arch=compute_70,code=sm_70;-gencode;arch=compute_75,code=sm_75
  - CuDNN 7.6.3
  - Magma 2.5.2
  - Build settings: BLAS=MKL, BUILD_TYPE=Release, CXX_FLAGS= -Wno-deprecated -fvisibility-inlines-hidden -DUSE_PTHREADPOOL -fopenmp -DNDEBUG -DUSE_FBGEMM -DUSE_QNNPACK -DUSE_PYTORCH_QNNPACK -DUSE_XNNPACK -DUSE_VULKAN_WRAPPER -O2 -fPIC -Wno-narrowing -Wall -Wextra -Werror=return-type -Wno-missing-field-initializers -Wno-type-limits -Wno-array-bounds -Wno-unknown-pragmas -Wno-sign-compare -Wno-unused-parameter -Wno-unused-variable -Wno-unused-function -Wno-unused-result -Wno-unused-local-typedefs -Wno-strict-overflow -Wno-strict-aliasing -Wno-error=deprecated-declarations -Wno-stringop-overflow -Wno-psabi -Wno-error=pedantic -Wno-error=redundant-decls -Wno-error=old-style-cast -fdiagnostics-color=always -faligned-new -Wno-unused-but-set-variable -Wno-maybe-uninitialized -fno-math-errno -fno-trapping-math -Werror=format -Wno-stringop-overflow, PERF_WITH_AVX=1, PERF_WITH_AVX2=1, PERF_WITH_AVX512=1, USE_CUDA=ON, USE_EXCEPTION_PTR=1, USE_GFLAGS=OFF, USE_GLOG=OFF, USE_MKL=ON, USE_MKLDNN=ON, USE_MPI=OFF, USE_NCCL=ON, USE_NNPACK=ON, USE_OPENMP=ON,

Result
Size (MB): 438.021641
Size (MB): 181.502781
Evaluating: 100%|████████████████████████████████████████████████████████████████████████████████| 51/51 [03:19<00:00,  3.92s/it]
{'acc': 0.8602941176470589, 'f1': 0.9018932874354562, 'acc_and_f1': 0.8810937025412575}
Evaluate total time (seconds): 200.0
Evaluating: 100%|████████████████████████████████████████████████████████████████████████████████| 51/51 [01:57<00:00,  2.31s/it]
{'acc': 0.8578431372549019, 'f1': 0.8999999999999999, 'acc_and_f1': 0.878921568627451}
Evaluate total time (seconds): 117.6

In this case, I can get considerable speed up with same env_setting&code;
I think that Intel broadwell&haswell processors are related with this issue;