On 11/26/18 7:55 PM, xingyi wu wrote: > hello guys, > We have upgraded kernel and found many exited optimizations in > writeback flow control, including set max writeback rate when the > backend device is idle. this is very helpful to keep a smaller size of > dirty data and when large amount of IO requests come, the caching system > can store more data. > But in our system, backend device is unlike to be totally idle > because our clients always keep sending IO requests to the frondend > device, even though sometimes the rate could be rather slow(like several > kb/s), in such case, the backend device is rather "idle" and we hope to > have higher writeback to keep smaller dirty data size. Does it make > sense? Is is possible to implement? Thanks. > It is possible to implement a minimum writeback rate, and let the minimum value of self-adopted writeback rate always being >= minimum_writeback_rate. But a larger writeback rate may increase regular I/O latency, so it is not recommended when there is no much dirty data. Could you please to provide a real case why you care about writeback performance more than regular I/O performance ? Thanks. Coly Li
