How to increase read and write speed in shared memory mode?

Xavier AGX on custom carrier, Jetpack_5.1.1 / R35.2.1 / Kernel 5.10

In shared memory mode, it can work normally,

I followed the directions here: Increasing size of BAR0 in Endpoint Mode - #3 by WayneWWW

BAR0_SIZE can be set to 2G

Region 0: Memory at 1f80000000 (32-bit, non-prefetchable) [size=2G]

Region 2: Memory at 1c00000000 (64-bit, prefetchable) [size=128K]

Region 4: Memory at 1f40000000 (64-bit, non-prefetchable) [size=1M]

I opened a 1GB file, read the data content, and write it into the memory.

The actual writing rate in the test was only 21 MB/s.

How can I increase the transfer rate?