On 11/29/18 11:16 AM, fangchen sun wrote: > hello guys, > > I want to change writeback_percent in bcache, but it seems that the > value is hardcoded in the bcache drive code. Why is writeback_percent > capped at 40 ？ Can I set it 60 or higher percent? What are risks of > higher percent ? I just posted a 5 patches series titled "writeback performance tuning options", which may permit people to set writeback percent to 70 at most for research purpose. Generally I don't suggest to set a higher writeback percent, a lower writeback percent number may start writeback thread earlier and have a more smooth I/O latency number. Too much dirty data on cache device may have negative impact for most of work load. You may try the patch set with a higher writeback percent, but unless you have a strong reason, I will always to use the default values firstly. Thanks. Coly Li
