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    Subject[RFC][PATCH 09/22] sched: add period support for -deadline tasks
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    Make it possible to specify a period (different or equal than
    deadline) for -deadline tasks.

    Signed-off-by: Harald Gustafsson <harald.gustafsson@ericsson.com>
    Signed-off-by: Dario Faggioli <raistlin@linux.it>
    ---
    include/linux/sched.h | 1 +
    kernel/sched.c | 12 +++++++++++-
    kernel/sched_dl.c | 8 ++++++--
    3 files changed, 18 insertions(+), 3 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index f25d3a6..83fa2b5 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1251,6 +1251,7 @@ struct sched_dl_entity {
    */
    u64 dl_runtime; /* maximum runtime for each instance */
    u64 dl_deadline; /* relative deadline of each instance */
    + u64 dl_period; /* separation of two instances (period) */

    /*
    * Actual scheduling parameters. Initialized with the values above,
    diff --git a/kernel/sched.c b/kernel/sched.c
    index 7f0780c..4491f7d 100644
    --- a/kernel/sched.c
    +++ b/kernel/sched.c
    @@ -2708,6 +2708,7 @@ static void __sched_fork(struct task_struct *p)
    hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    p->dl.dl_runtime = p->dl.runtime = 0;
    p->dl.dl_deadline = p->dl.deadline = 0;
    + p->dl.dl_period = 0;
    p->dl.flags = 0;

    INIT_LIST_HEAD(&p->rt.run_list);
    @@ -4789,6 +4790,10 @@ __setparam_dl(struct task_struct *p, const struct sched_param_ex *param_ex)
    init_dl_task_timer(dl_se);
    dl_se->dl_runtime = timespec_to_ns(&param_ex->sched_runtime);
    dl_se->dl_deadline = timespec_to_ns(&param_ex->sched_deadline);
    + if (timespec_to_ns(&param_ex->sched_period) != 0)
    + dl_se->dl_period = timespec_to_ns(&param_ex->sched_period);
    + else
    + dl_se->dl_period = dl_se->dl_deadline;
    dl_se->flags = param_ex->sched_flags;
    dl_se->dl_throttled = 0;
    dl_se->dl_new = 1;
    @@ -4802,6 +4807,7 @@ __getparam_dl(struct task_struct *p, struct sched_param_ex *param_ex)
    param_ex->sched_priority = p->rt_priority;
    param_ex->sched_runtime = ns_to_timespec(dl_se->dl_runtime);
    param_ex->sched_deadline = ns_to_timespec(dl_se->dl_deadline);
    + param_ex->sched_period = ns_to_timespec(dl_se->dl_period);
    param_ex->sched_flags = dl_se->flags;
    param_ex->curr_runtime = ns_to_timespec(dl_se->runtime);
    param_ex->curr_deadline = ns_to_timespec(dl_se->deadline);
    @@ -4810,7 +4816,8 @@ __getparam_dl(struct task_struct *p, struct sched_param_ex *param_ex)
    /*
    * This function validates the new parameters of a -deadline task.
    * We ask for the deadline not being zero, and greater or equal
    - * than the runtime.
    + * than the runtime, as well as the period of being zero or
    + * not greater than deadline.
    */
    static bool
    __checkparam_dl(const struct sched_param_ex *prm, bool kthread)
    @@ -4822,6 +4829,9 @@ __checkparam_dl(const struct sched_param_ex *prm, bool kthread)
    return kthread;

    return timespec_to_ns(&prm->sched_deadline) != 0 &&
    + (timespec_to_ns(&prm->sched_period) == 0 ||
    + timespec_compare(&prm->sched_period,
    + &prm->sched_deadline) >= 0) &&
    timespec_compare(&prm->sched_deadline,
    &prm->sched_runtime) >= 0;
    }
    diff --git a/kernel/sched_dl.c b/kernel/sched_dl.c
    index 1bb4308..31fb771 100644
    --- a/kernel/sched_dl.c
    +++ b/kernel/sched_dl.c
    @@ -263,7 +263,7 @@ 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;
    }

    @@ -290,7 +290,11 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
    * assigned (function returns true if it can).
    *
    * For this to hold, we must check if:
    - * runtime / (deadline - t) < dl_runtime / dl_deadline .
    + * runtime / (deadline - t) < dl_runtime / dl_period .
    + *
    + * 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)
    {
    --
    1.7.2.3

    --
    <<This happens because I choose it to happen!>> (Raistlin Majere)
    ----------------------------------------------------------------------
    Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy)
    http://blog.linux.it/raistlin / raistlin@ekiga.net /
    dario.faggioli@jabber.org
    [unhandled content-type:application/pgp-signature]
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