From 755378a47192a3d1f7c3a8ca6c15c1cf76de0af2 Mon Sep 17 00:00:00 2001 From: Harald Gustafsson Date: Thu, 7 Nov 2013 14:43:40 +0100 Subject: sched/deadline: Add period support for SCHED_DEADLINE tasks Make it possible to specify a period (different or equal than deadline) for -deadline tasks. Relative deadlines (D_i) are used on task arrivals to generate new scheduling (absolute) deadlines as "d = t + D_i", and periods (P_i) to postpone the scheduling deadlines as "d = d + P_i" when the budget is zero. This is in general useful to model (and schedule) tasks that have slow activation rates (long periods), but have to be scheduled soon once activated (short deadlines). Signed-off-by: Harald Gustafsson Signed-off-by: Dario Faggioli Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1383831828-15501-7-git-send-email-juri.lelli@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/deadline.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'kernel/sched/deadline.c') diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 21f58d261134..3958bc576d67 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -289,7 +289,7 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se) * arbitrary large. */ while (dl_se->runtime <= 0) { - dl_se->deadline += dl_se->dl_deadline; + dl_se->deadline += dl_se->dl_period; dl_se->runtime += dl_se->dl_runtime; } @@ -329,9 +329,13 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se) * * This function returns true if: * - * runtime / (deadline - t) > dl_runtime / dl_deadline , + * runtime / (deadline - t) > dl_runtime / dl_period , * * IOW we can't recycle current parameters. + * + * Notice that the bandwidth check is done against the period. For + * task with deadline equal to period this is the same of using + * dl_deadline instead of dl_period in the equation above. */ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t) { @@ -355,7 +359,7 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t) * of anything below microseconds resolution is actually fiction * (but still we want to give the user that illusion >;). */ - left = (dl_se->dl_deadline >> 10) * (dl_se->runtime >> 10); + left = (dl_se->dl_period >> 10) * (dl_se->runtime >> 10); right = ((dl_se->deadline - t) >> 10) * (dl_se->dl_runtime >> 10); return dl_time_before(right, left); -- cgit v1.2.3