在 2022/11/26 14:08, Yu Kuai 写道:
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?
Sorry that should be nr_requests <= queue_depth.
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
.
.
