From: Luca Abeni <luca.ab...@santannapisa.it>
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
utilization).
Hence, this commit modifies the runtime accounting rule in
update_curr_dl() to implement the GRUB rule.
Signed-off-by: Luca Abeni <luca.ab...@santannapisa.it>
Tested-by: Daniel Bristot de Oliveira <bris...@redhat.com>
---
kernel/sched/deadline.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 238713e..6035311 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -862,6 +862,19 @@ 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).
*/
@@ -903,6 +916,7 @@ static void update_curr_dl(struct rq *rq)
sched_rt_avg_update(rq, delta_exec);
+ delta_exec = grub_reclaim(delta_exec, rq);
dl_se->runtime -= delta_exec;
throttle:
--
2.7.4
