First Test: dm-crypt

This test is to test the read speed on GPU reading file on different given block size:

Block Size           CPU              GPU         HDD                       RAM           GRAM
4 KB                    20MB/s         30MB/s     5400rpm                DDR2          GDDR3
16KB                   23MB/s         37MB/s     5400rpm                DDR2           GDDR3
64KB                   29MB/s         38.5MB/s   5400rpm               DDR2          GDDR3
4 KB                    21MB/s         29MB/s     7200rpm                DDR2           GDDR3
16KB                   24.5MB/s      40MB/s     7200rpm                DDR2          GDDR3
64KB                   31MB/s         39MB/s      7200rpm               DDR2          GDDR3



From this result, GPU has a better performance than CPU, however, the HDD has little influence on the performance.  However, the main memory and memory of GPU may be the bottleneck.
Also, as 
KGPU_BUF_SIZE*2 < Size of Your Video
I set it to 200 in
kgpu/kgpu.h