Tejun Heo c421a3eb2e blk-iocost: revamp debt handling
Debt handling had several issues.

* How much inuse a debtor carries wasn't clearly defined. inuse would be
  driven down over time from not issuing IOs but it'd be better to clamp it
  to minimum immediately once in debt.

* How much can be paid off was determined by hweight_inuse. As inuse was
  driven down, the payment amount would fall together regardless of the
  debtor's active weight. This means that the debtors were punished harshly.

* ioc_rqos_merge() wasn't calling blkcg_schedule_throttle() after
  iocg_kick_delay().

This patch revamps debt handling so that

* Debt handling owns inuse for iocgs in debt and keeps them at zero.

* Payment amount is determined by hweight_active. This is more deterministic
  and safer than hweight_inuse but still far from ideal in that it doesn't
  factor in possible donations from other iocgs for debt payments. This
  likely needs further improvements in the future.

* iocg_rqos_merge() now calls blkcg_schedule_throttle() as necessary.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andy Newell <newella@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01 19:38:32 -06:00
..
2020-08-18 07:48:08 -07:00
2020-08-18 07:48:08 -07:00
2020-08-18 07:48:08 -07:00
2020-08-21 17:14:27 -06:00
2020-09-01 19:38:32 -06:00
2020-08-03 11:57:03 -07:00
2020-03-17 20:55:21 +01:00
2020-05-29 16:30:39 -06:00
2020-08-16 20:07:12 -07:00
2020-01-03 09:33:21 +01:00
2020-01-06 20:59:04 -07:00