[RFC v4 4/6] sched/deadline: implement GRUB accounting
From: Luca Abeni
Date: Fri Dec 30 2016 - 06:34:09 EST
From: Luca Abeni <luca.abeni@xxxxxxxx>
According to the GRUB (Greedy Reclaimation of Unused Bandwidth)
reclaiming algorithm, the runtime is not decreased as "dq = -dt",
but as "dq = -Uact dt" (where Uact is the per-runqueue active
Hence, this commit modifies the runtime accounting rule in
update_curr_dl() to implement the GRUB rule.
Signed-off-by: Luca Abeni <luca.abeni@xxxxxxxx>
kernel/sched/deadline.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index c087c3d..361887b 100644
@@ -764,6 +764,19 @@ int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
+ * This function implements the GRUB accounting rule:
+ * according to the GRUB reclaiming algorithm, the runtime is
+ * not decreased as "dq = -dt", but as "dq = -Uact dt", where
+ * Uact is the (per-runqueue) active utilization.
+ * Since rq->dl.running_bw contains Uact * 2^20, the result
+ * has to be shifted right by 20.
+u64 grub_reclaim(u64 delta, struct rq *rq)
+ return (delta * rq->dl.running_bw) >> 20;
* Update the current task's runtime statistics (provided it is still
* a -deadline task and has not been removed from the dl_rq).
@@ -805,6 +818,7 @@ static void update_curr_dl(struct rq *rq)
+ delta_exec = grub_reclaim(delta_exec, rq);
dl_se->runtime -= delta_exec;