USB 端口读写性能测试：
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读测试：
sync && echo 3 > /proc/sys/vm/drop_caches; dd if=/mnt/media_rw/F004-BB9B/file.bin of=/dev/zero bs=4096 count=524288
写测试：
sync && echo 3 > /proc/sys/vm/drop_caches; dd if=/dev/zero of=/mnt/media_rw/F004-BB9B/file.bin bs=4096 count=524288
sync && echo 3 > /proc/sys/vm/drop_caches; dd if=/dev/zero of=./sdg bs=4096 count=131072
标签：USB,读写,sync,echo,zero,Linux,proc,4096 From： https://www.cnblogs.com/pypyn/p/17133699.html