[PATCH 2/2] block: Switch from BFQ-v6r2 for 3.3.0 to BFQ-v7 for 3.3.0
 - second part

Improvements:

- An application must be non-greedy to be deemed as soft real-time (it is
  one of the conditions to meet). The condition is checked by controlling
  whether a long-enough time interval, by default HZ/125 seconds, elapsed
  from when the queue associated to the application became idle, to when
  the queue becomes backlogged again. Elapsed time is measured in
  jiffies.
  This control easily generates false positives in the following two
  cases (especially if both cases occur):
  1) If HZ is so low that the duration of a jiffie is comparable to or
     higher than the above reference time interval. This happens, e.g.,
     on slow devices with HZ=100.
  2) If jiffies, instead of increasing at a constant rate, may stop
     increasing for some time, then suddenly 'jump' by several units to
     recover the lost increments. This seems to happen, e.g., in virtual
     machines.
  This commit adds a few jiffies to the above reference time interval.
  We found the number of jiffies to add experimentally. In particular,
  according to our experiments, the number of jiffies added by this
  commit seems to make the filter quite precise also in embedded systems
  and KVM/QEMU virtual machines.

Signed-off-by: Paolo Valente <p.valente@virtualopensystems.com>
Signed-off-by: Alexander Spyridakis <a.spyridakis@virtualopensystems.com>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>