diff options
Diffstat (limited to 'kernel/sched/deadline.c')
| -rw-r--r-- | kernel/sched/deadline.c | 40 |
1 files changed, 22 insertions, 18 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 6c6a1f099d61..7d2f05778060 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -955,26 +955,30 @@ 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^BW_SHIFT, the result - * has to be shifted right by BW_SHIFT. - * To reclaim only a fraction Umax of the CPU time, the - * runtime accounting rule is modified as - * "dq = -Uact / Umax dt"; since rq->dl.bw_ratio contains - * 2^RATIO_SHIFT / Umax, delta is multiplied by bw_ratio and shifted - * right by RATIO_SHIFT. - * Since delta is a 64 bit variable, to have an overflow its value - * should be larger than 2^(64 - 20 - 8), which is more than 64 seconds. - * So, overflow is not an issue here. + * not decreased as "dq = -dt", but as "dq = -max{u, (1 - Uinact)} dt", + * where u is the utilization of the task and Uinact is the + * (per-runqueue) inactive utilization, computed as the difference + * between the "total runqueue utilization" and the runqueue + * active utilization. + * Since rq->dl.running_bw and rq->dl.this_bw contain utilizations + * multiplied by 2^BW_SHIFT, the result has to be shifted right by BW_SHIFT. */ -u64 grub_reclaim(u64 delta, struct rq *rq) +u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se) { - delta *= rq->dl.running_bw; - delta *= rq->dl.bw_ratio; - delta >>= BW_SHIFT + RATIO_SHIFT; + u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot - Uact */ + u64 u_act; - return delta; + /* + * Instead of computing max{u, (1 - u_inact)}, we compare + * u_inact with 1 - u, because u_inact can be larger than 1 + * (so, 1 - u_inact would be negative leading to wrong results) + */ + if (u_inact > BW_UNIT - dl_se->dl_bw) + u_act = dl_se->dl_bw; + else + u_act = BW_UNIT - u_inact; + + return (delta * u_act) >> BW_SHIFT; } /* @@ -1020,7 +1024,7 @@ static void update_curr_dl(struct rq *rq) sched_rt_avg_update(rq, delta_exec); if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) - delta_exec = grub_reclaim(delta_exec, rq); + delta_exec = grub_reclaim(delta_exec, rq, &curr->dl); dl_se->runtime -= delta_exec; throttle: |