lkml.org 
[lkml]   [2010]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [RFC][PATCH 10/11] sched: add bandwidth management for sched_dl.
    From
    Date
    On Sun, 2010-02-28 at 20:27 +0100, Raistlin wrote:
    > @@ -2063,6 +2210,30 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
    > return delta < (s64)sysctl_sched_migration_cost;
    > }
    >
    > +/*
    > + * When dealing with a -deadline task, we have to check if moving it to
    > + * a new CPU is possible or not. In fact, this is only true iff there
    > + * is enough bandwidth available on such CPU, otherwise we want the
    > + * whole migration progedure to fail over.
    > + */
    > +static inline
    > +bool __set_task_cpu_dl(struct task_struct *p, unsigned int cpu)
    > +{
    > + struct dl_bandwidth *dl_b = task_dl_bandwidth(p);
    > +
    > + raw_spin_lock(&dl_b->dl_runtime_lock);
    > + if (dl_b->dl_bw < dl_b->dl_total_bw[cpu] + p->dl.dl_bw) {
    > + raw_spin_unlock(&dl_b->dl_runtime_lock);
    > +
    > + return 0;
    > + }
    > + dl_b->dl_total_bw[task_cpu(p)] -= p->dl.dl_bw;
    > + dl_b->dl_total_bw[cpu] += p->dl.dl_bw;
    > + raw_spin_unlock(&dl_b->dl_runtime_lock);
    > +
    > + return 1;
    > +}
    > +
    > void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
    > {
    > #ifdef CONFIG_SCHED_DEBUG
    > @@ -2077,6 +2248,9 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
    > trace_sched_migrate_task(p, new_cpu);
    >
    > if (task_cpu(p) != new_cpu) {
    > + if (task_has_dl_policy(p) && !__set_task_cpu_dl(p, new_cpu))
    > + return;
    > +
    > p->se.nr_migrations++;
    > perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 1, NULL, 0);
    > }

    Yikes!!, I'm not sure we can sanely deal with set_task_cpu() doing that.

    I'd much rather see us never attempting set_task_cpu() when we know its
    not going to be possible.

    That also means that things like set_cpus_allowed_ptr() /
    sys_sched_setaffinity() will need to propagate the error back to their
    users, which in turn will need to be able to cope.



    \
     
     \ /
      Last update: 2010-04-15 09:31    [W:6.791 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site