On Friday 2013-02-22 20:28, Martin Svec wrote:
Yes, I've already tried the ROW scheduler. It helped for some low iodepths
depending on quantum settings but generally didn't solve the problem. I think
the key issue is that none of the schedulers can throttle I/O according to e.g.
average request roundtrip time. Shaohua Li is right here:
https://lkml.org/lkml/2012/12/11/598 -- as long as there's free room in
device's queue they blindly dispatch requests to it.
Which is exactly what I see in deadline scheduler fifo queues: There're no read
requests to be scheduled between writes because all readers are starving. So
the scheduler keeps dispatching writes using all the remaining capacity of
device queue. Which in turn worses the read starvation. Bigger queue depth and
bigger writeback cache means higher chance for read starvation even from a
Sounds just like the bufferbloat problem in networking.
Waiting for codel for the block layer :)