Hi,everyone.
I upgrade kernel form 3.14.x to 4.4.x recently on my ARM64 server. I create a RAID5 device with 8 disks on the server and have a dd test which like this "dd if=/dev/zero of=/dev/md5 bs=64K count=400000". Before upgrade it can reach 700M/s written and only 500M/s after upgrade. Then I disable the bitmap which means "mdadm create --bitmap=none", the speed can reach 800M/s with 4.4 kernel. I have a fast view on driver/md/bitmap.c and got no answer. I doubt X86 platform has the same question. So, what is the most difference between 3.14.x and 4.4.x about md driver. Where could I found the ChangeLog or commit about the driver. Any answer would be thankful.
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