In my case, the computer is run in a virtul machine, and the hard disk(SSD) reading speed limit is 400MB/s.

I use rsync to send a large number of small files(the number of files is 202111) to other computer.
without reading ahead files, the disk reading speed is under 50 MB/s.

I modify the rsync source code, use the posis api posix_fadvise(https://www.man7.org/linux/man-pages/man2/posix_fadvise.2.html) to read ahead files in batches.
posix_fadvise will read file to system page cache，then rsync can read file from page cache。

Test result shows that the disk reading speed is near 400 MB/s，and it significantly reduce the time for file reading.

The optimized rsync run in production environment for several months steadily, without any crash.

Because the company‘s rules, I can not share the optimized source code to github. so i share this idea to all.