linux-kernel - [RFCv2 PATCH 15/23] sched, cpufreq: Introduce current cpu compute capacity into scheduler

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Date:	Thu,  3 Jul 2014 17:26:02 +0100
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	peterz@...radead.org, mingo@...nel.org
Cc:	rjw@...ysocki.net, vincent.guittot@...aro.org,
	daniel.lezcano@...aro.org, preeti@...ux.vnet.ibm.com,
	Dietmar.Eggemann@....com, pjt@...gle.com
Subject: [RFCv2 PATCH 15/23] sched, cpufreq: Introduce current cpu compute capacity into scheduler

The scheduler is currently unaware of frequency changes and the current
compute capacity offered by the cpus. This patch is not the solution.
It is a hack to give us something to experiment with for now.

A proper solution could be based on the frequency invariant load
tracking proposed in the past: https://lkml.org/lkml/2013/4/16/289
The best way to get current compute capacity is likely to be
architecture specific. A potential solution is therefore to let the
architecture implement get_curr_capacity() instead.

This patch should _not_ be considered safe.

Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
---
 drivers/cpufreq/cpufreq.c |    2 ++
 include/linux/sched.h     |    2 ++
 kernel/sched/fair.c       |   11 +++++++++++
 kernel/sched/sched.h      |    2 ++
 4 files changed, 17 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index abda660..a2b788d 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -28,6 +28,7 @@
 #include <linux/slab.h>
 #include <linux/suspend.h>
 #include <linux/tick.h>
+#include <linux/sched.h>
 #include <trace/events/power.h>
 
 /**
@@ -315,6 +316,7 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
 		pr_debug("FREQ: %lu - CPU: %lu\n",
 			 (unsigned long)freqs->new, (unsigned long)freqs->cpu);
 		trace_cpu_frequency(freqs->new, freqs->cpu);
+		set_curr_capacity(freqs->cpu, (freqs->new*1024)/policy->max);
 		srcu_notifier_call_chain(&cpufreq_transition_notifier_list,
 				CPUFREQ_POSTCHANGE, freqs);
 		if (likely(policy) && likely(policy->cpu == freqs->cpu))
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e5d8d57..faebd87 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -3025,4 +3025,6 @@ static inline unsigned long rlimit_max(unsigned int limit)
 	return task_rlimit_max(current, limit);
 }
 
+void set_curr_capacity(int cpu, long capacity);
+
 #endif
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 37e9ea1..9720f04 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7564,9 +7564,20 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
 	atomic64_set(&cfs_rq->decay_counter, 1);
 	atomic_long_set(&cfs_rq->removed_load, 0);
 	atomic_long_set(&cfs_rq->uw_removed_load, 0);
+	atomic_long_set(&cfs_rq->curr_capacity, 1024);
 #endif
 }
 
+void set_curr_capacity(int cpu, long capacity)
+{
+	atomic_long_set(&cpu_rq(cpu)->cfs.curr_capacity, capacity);
+}
+
+static inline unsigned long get_curr_capacity(int cpu)
+{
+	return atomic_long_read(&cpu_rq(cpu)->cfs.curr_capacity);
+}
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void task_move_group_fair(struct task_struct *p, int on_rq)
 {
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 455d152..a6d5239 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -342,6 +342,8 @@ struct cfs_rq {
 	u64 last_decay;
 	atomic_long_t removed_load, uw_removed_load;
 
+	atomic_long_t curr_capacity;
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	/* Required to track per-cpu representation of a task_group */
 	u32 tg_runnable_contrib;
-- 
1.7.9.5


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