From: Tang Junhui <tang.junhui@xxxxxxxxxx> On Tue, Nov 21, 2017 at 06:50:32PM +0800, tang.junhui@xxxxxxxxxx wrote: > > From: Tang Junhui <tang.junhui@xxxxxxxxxx> > > > > Currently in pick_data_bucket(), though we keep multiple buckets open > > for writes, and try to segregate different write streams for better > > cache utilization: first we look for a bucket where the last write to > > it was sequential with the current write, and failing that we look > > for a bucket that was last usedby the same task. > > > > But actually, in such scenario that there are some flash devices > > , and some backend bcache devices, when many tasks request these > > flash devices and backend bcache devices, the write IOs may still > > fall to the same bucket as bellow bucket: > > | bcache data | flash data | bcache data | bcache data| flash data| > > then after writeback of these backend bcache devices, the bucket would > > be like bellow bucket: > > | free | flash data | free | free | flash data | > This patch doesn't make any sense - open_buckets are only for allocations and > writes to the SSD. Thank you for your quick respond, It's true that open_buckets are only for allocations and writes to the SSD, but in writeback mode, data from flash devices and backend bcache devices are all write to bucket(SSD). This patch add a separate open bucket list for flash devices, so data from flash devices and backend bcache devices can store in different buckets. Thanks, Tang
