On Sat, Jul 18, 2020 at 2:28 AM Yufen Yu <yuyufen@xxxxxxxxxx> wrote: > > 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 > > Normally, using default stripe_size can get better performance. So, NeilBrown > have suggested just to fix the it as 4096. But, out test result shows that > a big value of stripe_size may have better performance when size of issued > IOs are mostly bigger than 4096. Thus, in this patchset, we still want to > set stripe_size as a configurable value. > > This patchset just set STRIPE_SIZE as a configurable value for "PAGE_SIZE != 4096" > system, likely arm64 with 'PAGE_SIZE=64KB'. It doesn't make any difference for > 'PAGE_SIZE == 4096' system, likely x86. > > To save memory used by stripe_head, I will send the related optimiation patchset later. Applied to md-next. Thanks!
