| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20150331231836.GA10760@kernel>
Date: Wed, 1 Apr 2015 07:18:36 +0800
From: Wanpeng Li <wanpeng.li@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@....com>
Cc: Wanpeng Li <wanpeng.li@...ux.intel.com>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/deadline: Use IPI to trigger DL task push
migration instead of pulling
On Mon, Mar 30, 2015 at 09:41:40AM -0400, Steven Rostedt wrote:
>On Mon, 30 Mar 2015 07:07:10 +0800
>Wanpeng Li <wanpeng.li@...ux.intel.com> wrote:
>
>> +static int find_next_push_cpu(struct rq *rq)
>> +{
>> + struct rq *next_rq;
>> + int cpu;
>> +
>> + while (1) {
>> + cpu = dlo_next_cpu(rq);
>> + if (cpu >= nr_cpu_ids)
>> + break;
>> + next_rq = cpu_rq(cpu);
>> +
>> + /* Make sure the next rq can push to this rq */
>> + if (dl_time_before(next_rq->dl.earliest_dl.next,
>> + rq->dl.earliest_dl.curr))
>> + break;
>> + }
>> +
>> + return cpu;
>> +}
>> +
>
>Is it possible that we don't duplicate the code and that we can find a
>way to share the code between rt and dl? It's not that trivial to just
>cut and paste. If a bug is found in one, it most likely wont be ported
>to the other.
>
>The best is if we can share the code here some way. Perhaps have a
>single IPI that checks both rt and dl?
Peter, Juri, what's your ideas? ;)
Regards,
Wanpeng Li
>
>-- Steve
>
>> +#define RT_PUSH_IPI_EXECUTING 1
>> +#define RT_PUSH_IPI_RESTART 2
>> +
>> +static void tell_cpu_to_push(struct rq *rq)
>> +{
>> + int cpu;
>> +
>> + if (rq->dl.push_flags & RT_PUSH_IPI_EXECUTING) {
>> + raw_spin_lock(&rq->dl.push_lock);
>> + /* Make sure it's still executing */
>> + if (rq->dl.push_flags & RT_PUSH_IPI_EXECUTING) {
>> + /*
>> + * Tell the IPI to restart the loop as things have
>> + * changed since it started.
>> + */
>> + rq->dl.push_flags |= RT_PUSH_IPI_RESTART;
>> + raw_spin_unlock(&rq->dl.push_lock);
>> + return;
>> + }
>> + raw_spin_unlock(&rq->dl.push_lock);
>> + }
>> +
>> + /* When here, there's no IPI going around */
>> +
>> + rq->dl.push_cpu = rq->cpu;
>> + cpu = find_next_push_cpu(rq);
>> + if (cpu >= nr_cpu_ids)
>> + return;
>> +
>> + rq->dl.push_flags = RT_PUSH_IPI_EXECUTING;
>> +
>> + irq_work_queue_on(&rq->dl.push_work, cpu);
>> +}
>> +
>> +/* Called from hardirq context */
>> +static void try_to_push_tasks(void *arg)
>> +{
>> + struct dl_rq *dl_rq = arg;
>> + struct rq *rq, *src_rq;
>> + int this_cpu;
>> + int cpu;
>> +
>> + this_cpu = dl_rq->push_cpu;
>> +
>> + /* Paranoid check */
>> + BUG_ON(this_cpu != smp_processor_id());
>> +
>> + rq = cpu_rq(this_cpu);
>> + src_rq = rq_of_dl_rq(dl_rq);
>> +
>> +again:
>> + if (has_pushable_dl_tasks(rq)) {
>> + raw_spin_lock(&rq->lock);
>> + push_dl_task(rq);
>> + raw_spin_unlock(&rq->lock);
>> + }
>> +
>> + /* Pass the IPI to the next rt overloaded queue */
>> + raw_spin_lock(&dl_rq->push_lock);
>> + /*
>> + * If the source queue changed since the IPI went out,
>> + * we need to restart the search from that CPU again.
>> + */
>> + if (dl_rq->push_flags & RT_PUSH_IPI_RESTART) {
>> + dl_rq->push_flags &= ~RT_PUSH_IPI_RESTART;
>> + dl_rq->push_cpu = src_rq->cpu;
>> + }
>> +
>> + cpu = find_next_push_cpu(src_rq);
>> +
>> + if (cpu >= nr_cpu_ids)
>> + dl_rq->push_flags &= ~RT_PUSH_IPI_EXECUTING;
>> + raw_spin_unlock(&dl_rq->push_lock);
>> +
>> + if (cpu >= nr_cpu_ids)
>> + return;
>> +
>> + /*
>> + * It is possible that a restart caused this CPU to be
>> + * chosen again. Don't bother with an IPI, just see if we
>> + * have more to push.
>> + */
>> + if (unlikely(cpu == rq->cpu))
>> + goto again;
>> +
>> + /* Try the next RT overloaded CPU */
>> + irq_work_queue_on(&dl_rq->push_work, cpu);
>> +}
>> +
>> +static void push_irq_work_func(struct irq_work *work)
>> +{
>> + struct dl_rq *dl_rq = container_of(work, struct dl_rq, push_work);
>> +
>> + try_to_push_tasks(dl_rq);
>> +}
>> +#endif /* HAVE_RT_PUSH_IPI */
>> +
>> static int pull_dl_task(struct rq *this_rq)
>> {
>> int this_cpu = this_rq->cpu, ret = 0, cpu;
>> @@ -1432,6 +1602,13 @@ static int pull_dl_task(struct rq *this_rq)
>> */
>> smp_rmb();
>>
>> +#ifdef HAVE_RT_PUSH_IPI
>> + if (sched_feat(RT_PUSH_IPI)) {
>> + tell_cpu_to_push(this_rq);
>> + return 0;
>> + }
>> +#endif
>> +
>> for_each_cpu(cpu, this_rq->rd->dlo_mask) {
>> if (this_cpu == cpu)
>> continue;
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index dd532c5..87a937c 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -500,6 +500,12 @@ struct dl_rq {
>> */
>> struct rb_root pushable_dl_tasks_root;
>> struct rb_node *pushable_dl_tasks_leftmost;
>> +#ifdef HAVE_RT_PUSH_IPI
>> + int push_flags;
>> + int push_cpu;
>> + struct irq_work push_work;
>> + raw_spinlock_t push_lock;
>> +#endif
>> #else
>> struct dl_bw dl_bw;
>> #endif
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists