On 01/02/2018 12:53 AM, tang.junhui@xxxxxxxxxx wrote: > If no front-end I/O coming, would this cause write-back IOs one by one > (one write-back IO issued must after the completion of the previous IO)? > though with zero delay time, is the write-back performance still good? Yes-- this speeds up writeback during idle from 4k/sec to about 10MB/sec on my slow 5400RPM disk. (It writes back at about 20MB/sec with deep queues in the same scenario). So in this case it's about 2500x faster than current idle writeback, but half as fast as writeback with full device utilization. With only one I/O outstanding at a time, if front-end I/O starts latency for the first request is still good. > Thanks, > Tang Junhui Mike
