diff options
| -rw-r--r-- | include/linux/sched.h | 1 | ||||
| -rw-r--r-- | kernel/sched/deadline.c | 23 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 33 |
3 files changed, 33 insertions, 24 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index f89313b150e6..e4ce0a76831e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -706,7 +706,6 @@ struct sched_dl_entity { unsigned int dl_defer : 1; unsigned int dl_defer_armed : 1; unsigned int dl_defer_running : 1; - unsigned int dl_server_idle : 1; /* * Bandwidth enforcement timer. Each -deadline task has its diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 5a5080b3a670..72c1f72463c7 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1571,10 +1571,8 @@ void dl_server_update_idle_time(struct rq *rq, struct task_struct *p) void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec) { /* 0 runtime = fair server disabled */ - if (dl_se->dl_runtime) { - dl_se->dl_server_idle = 0; + if (dl_se->dl_runtime) update_curr_dl_se(dl_se->rq, dl_se, delta_exec); - } } void dl_server_start(struct sched_dl_entity *dl_se) @@ -1602,20 +1600,6 @@ void dl_server_stop(struct sched_dl_entity *dl_se) dl_se->dl_server_active = 0; } -static bool dl_server_stopped(struct sched_dl_entity *dl_se) -{ - if (!dl_se->dl_server_active) - return true; - - if (dl_se->dl_server_idle) { - dl_server_stop(dl_se); - return true; - } - - dl_se->dl_server_idle = 1; - return false; -} - void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq, dl_server_pick_f pick_task) { @@ -2384,10 +2368,7 @@ again: if (dl_server(dl_se)) { p = dl_se->server_pick_task(dl_se); if (!p) { - if (!dl_server_stopped(dl_se)) { - dl_se->dl_yielded = 1; - update_curr_dl_se(rq, dl_se, 0); - } + dl_server_stop(dl_se); goto again; } rq->dl_server = dl_se; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index f10d6277dca1..cf2109b67f9a 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -371,10 +371,39 @@ extern s64 dl_scaled_delta_exec(struct rq *rq, struct sched_dl_entity *dl_se, s6 * dl_server_update() -- called from update_curr_common(), propagates runtime * to the server. * - * dl_server_start() - * dl_server_stop() -- start/stop the server when it has (no) tasks. + * dl_server_start() -- start the server when it has tasks; it will stop + * automatically when there are no more tasks, per + * dl_se::server_pick() returning NULL. + * + * dl_server_stop() -- (force) stop the server; use when updating + * parameters. * * dl_server_init() -- initializes the server. + * + * When started the dl_server will (per dl_defer) schedule a timer for its + * zero-laxity point -- that is, unlike regular EDF tasks which run ASAP, a + * server will run at the very end of its period. + * + * This is done such that any runtime from the target class can be accounted + * against the server -- through dl_server_update() above -- such that when it + * becomes time to run, it might already be out of runtime and get deferred + * until the next period. In this case dl_server_timer() will alternate + * between defer and replenish but never actually enqueue the server. + * + * Only when the target class does not manage to exhaust the server's runtime + * (there's actualy starvation in the given period), will the dl_server get on + * the runqueue. Once queued it will pick tasks from the target class and run + * them until either its runtime is exhaused, at which point its back to + * dl_server_timer, or until there are no more tasks to run, at which point + * the dl_server stops itself. + * + * By stopping at this point the dl_server retains bandwidth, which, if a new + * task wakes up imminently (starting the server again), can be used -- + * subject to CBS wakeup rules -- without having to wait for the next period. + * + * Additionally, because of the dl_defer behaviour the start/stop behaviour is + * naturally thottled to once per period, avoiding high context switch + * workloads from spamming the hrtimer program/cancel paths. */ extern void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec); extern void dl_server_start(struct sched_dl_entity *dl_se); |