Hi, Ming 在 2022/11/26 10:18, Ming Lei 写道:
If you want aggressive merge on sequential IO workload, the queue depth need to be a bit less, then more requests can be staggered into scheduler queue, and merge chance is increased.
But if nr_requests >= queue_depth, it seems to me elevator will have no effect, no request can be merged or sorted by scheduler, right?
If you want good perf on random IO perf, the queue depth needs to be deep enough to have enough parallelism for saturating SSD internal. But we don't recognize sequential/random IO pattern, and usually fixed queue depth is used.
Is it possible to use none elevator and set large queue_depth if nvme is used in this case? Thansk, Kuai
Thanks, Ming .
