On 2020/7/3 7:00, Song Liu wrote:

On Thu, Jul 2, 2020 at 5:05 AM Yufen Yu [off-list ref] wrote:

quoted

Hi, all

  For now, STRIPE_SIZE is equal to the value of PAGE_SIZE. That means, RAID5
  will issue each bio to disk at least 64KB when PAGE_SIZE is 64KB in arm64.
  However, filesystem usually issue bio in the unit of 4KB. Then, RAID5 may
  waste resource of disk bandwidth.

  To solve the problem, this patchset try to set stripe_size as a configuare
  value. The default value is 4096. We will add a new sysfs entry and set it
  by writing a new value, likely:

         echo 16384 > /sys/block/md1/md/stripe_size

Higher level question: do we need to support page size that is NOT 4kB
times power
of 2? Meaning, do we need to support 12kB, 20kB, 24kB, etc. If we only
supports, 4kB,
8kB, 16kB, 32kB, etc. some of the logic can be simpler.

Yeah, I think we just support 4kb, 8kb, 16kb, 32kb... is enough.
But Sorry that I don't know what logic can be simpler in current implementation.
I mean it also need to allocate page, and record page offset.

Thanks,
Yufen