exfat read speed was only 22MB/S in 4.9.112+sdcard ，but in vfat it can be 80MB/S

[lxiaogao]

HI namjaejeon：
Thanks for your code, I have tested your exfat code in qcom+4.9+sdcard，write speed was ok，but read speed was only about 22MB/S. Can you provide some suggestion about how to debug this,thank you again. one more question ,which exfat kernel version you based?

[namjaejeon]

Let me know how you measure performance. Have you dropped cache(echo 3 > /proc/sys/vm/drop_caches) before measuring performance ?

[namjaejeon]

and Does it depend on sdcard or kernel version? I wonder if the result will be different if HDD is used instead of sdcard and if you use the higher kernel version, It will show different results.

[lxiaogao]

HI namjaejeon, thanks for your reply. Yes I have dropped cache and try two sdcard[sandisk & samsung] , the read speed result was the same , following was the test commands :

drop cache
#echo 3 > /proc/sys/vm/drop_caches

read speed test：
time dd of=/dev/null if=/mnt/sdcard/1.bin bs=4096k count=200