On 08/21/2014 04:12 AM, Liu, Chuansheng wrote:
Hello Daniel,
-----Original Message-----
From: Daniel Lezcano [mailto:daniel.lezc...@linaro.org]
Sent: Thursday, August 21, 2014 9:54 AM
To: Liu, Chuansheng; l...@amacapital.net; pet...@infradead.org;
r...@rjwysocki.net; mi...@redhat.com
Cc: linux...@vger.kernel.org; linux-kernel@vger.kernel.org; Liu, Changcheng;
Wang, Xiaoming; Chakravarty, Souvik K
Subject: Re: [PATCH 1/3] sched: Add new API wake_up_if_idle() to wake up the
idle cpu
On 08/18/2014 10:37 AM, Chuansheng Liu wrote:
Implementing one new API wake_up_if_idle(), which is used to
wake up the idle CPU.
Is this patchset tested ? Did you check it solves the issue you were
facing ?
We have done the basic test, and found the cores can exit C0 quickly with this
patchset.
Basically once the _TIF_NEED_RESCHED is set, then the poll_idle() can be broken.
Please correct me if something is wrong, thanks.
Actually, it was not clear for me if this patch was a proposal or not.
I will review it.
Thanks
-- Daniel
Suggested-by: Andy Lutomirski <l...@amacapital.net>
Signed-off-by: Chuansheng Liu <chuansheng....@intel.com>
---
include/linux/sched.h | 1 +
kernel/sched/core.c | 16 ++++++++++++++++
2 files changed, 17 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 857ba40..3f89ac1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1024,6 +1024,7 @@ struct sched_domain_topology_level {
extern struct sched_domain_topology_level *sched_domain_topology;
extern void set_sched_topology(struct sched_domain_topology_level *tl);
+extern void wake_up_if_idle(int cpu);
#ifdef CONFIG_SCHED_DEBUG
# define SD_INIT_NAME(type) .name = #type
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1211575..adf104f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1620,6 +1620,22 @@ static void ttwu_queue_remote(struct
task_struct *p, int cpu)
}
}
+void wake_up_if_idle(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long flags;
+
+ if (set_nr_if_polling(rq->idle)) {
+ trace_sched_wake_idle_without_ipi(cpu);
+ } else {
+ raw_spin_lock_irqsave(&rq->lock, flags);
+ if (rq->curr == rq->idle)
+ smp_send_reschedule(cpu);
+ /* Else cpu is not in idle, do nothing here */
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
+ }
+}
+
bool cpus_share_cache(int this_cpu, int that_cpu)
{
return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
--
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--
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