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Date: Thu, 26 Jun 2014 18:09:37 +0900
From: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To: linux-kernel@...r.kernel.org
CC: Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
Frederic Weisbecker <fweisbec@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Arjan van de Ven <arjan@...ux.intel.com>,
Oleg Nesterov <oleg@...hat.com>,
Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
Denys Vlasenko <vda.linux@...glemail.com>
Subject: [PATCH 2/8] cputime, nohz: handle last_iowait for nohz
Now observer cpu can refer both of idle entry time and iowait exit
time of observed sleeping cpu, so observer can get idle/iowait time
of sleeping cpu by calculating cputimes not accounted yet.
Not-Tested-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
---
include/linux/sched.h | 1 +
kernel/sched/core.c | 27 +++++++++++++++++++++++++
kernel/time/tick-sched.c | 48 +++++++++++++++++++++++++++++++++------------
3 files changed, 63 insertions(+), 13 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 306f4f0..29e1af0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -168,6 +168,7 @@ extern int nr_processes(void);
extern unsigned long nr_running(void);
extern unsigned long nr_iowait(void);
extern unsigned long nr_iowait_cpu(int cpu);
+extern void nr_iowait_deltas(int cpu, ktime_t start, ktime_t now, ktime_t *iowait, ktime_t *idle);
extern unsigned long this_cpu_load(void);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e759238..814ee2e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2384,6 +2384,33 @@ unsigned long nr_iowait_cpu(int cpu)
return cpu_rq(cpu)->nr_iowait;
}
+/*
+ * nr_iowait_deltas - divide idle time into idle delta and iowait delta
+ *
+ * @start: time stamp at start of idle span
+ * @now: time stamp at end of idle span
+ * @iowait_delta: address to store calculated iowait
+ * @idle_delta: address to store calculated idle
+ */
+void nr_iowait_deltas(int cpu, ktime_t start, ktime_t now,
+ ktime_t *iowait_delta, ktime_t *idle_delta)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ raw_spin_lock(&rq->iowait_lock);
+ if (rq->nr_iowait || ktime_compare(rq->last_iowait, now) > 0) {
+ *iowait_delta = ktime_sub(now, start);
+ *idle_delta = ktime_set(0, 0);
+ } else if (ktime_compare(rq->last_iowait, start) > 0) {
+ *iowait_delta = ktime_sub(rq->last_iowait, start);
+ *idle_delta = ktime_sub(now, rq->last_iowait);
+ } else {
+ *iowait_delta = ktime_set(0, 0);
+ *idle_delta = ktime_sub(now, start);
+ }
+ raw_spin_unlock(&rq->iowait_lock);
+}
+
#ifdef CONFIG_SMP
/*
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 44eb187..8d23af5 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -408,16 +408,22 @@ static void tick_nohz_update_jiffies(ktime_t now)
static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
{
- ktime_t delta;
+ static const ktime_t ktime_zero = { .tv64 = 0 };
+ ktime_t iowait_delta = ktime_zero, idle_delta = ktime_zero;
write_seqcount_begin(&ts->idle_sleeptime_seq);
/* Updates the per cpu time idle statistics counters */
- delta = ktime_sub(now, ts->idle_entrytime);
- if (nr_iowait_cpu(smp_processor_id()) > 0)
- ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
- else
- ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+ if (ts->idle_active == 2) {
+ nr_iowait_deltas(smp_processor_id(), ts->idle_entrytime, now,
+ &iowait_delta, &idle_delta);
+ ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime,
+ iowait_delta);
+ } else {
+ idle_delta = ktime_sub(now, ts->idle_entrytime);
+ }
+ ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, idle_delta);
+
ts->idle_entrytime = now;
ts->idle_active = 0;
@@ -432,7 +438,13 @@ static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
write_seqcount_begin(&ts->idle_sleeptime_seq);
ts->idle_entrytime = now;
- ts->idle_active = 1;
+ /*
+ * idle_active:
+ * 0: cpu is not idle
+ * 1: cpu is performing idle
+ * 2: cpu is performing iowait and idle
+ */
+ ts->idle_active = 1 + !!nr_iowait_cpu(smp_processor_id());
write_seqcount_end(&ts->idle_sleeptime_seq);
sched_clock_idle_sleep_event();
@@ -467,10 +479,18 @@ u64 get_cpu_idle_time_us(int cpu, u64 *wall)
do {
seq = read_seqcount_begin(&ts->idle_sleeptime_seq);
-
- if (ts->idle_active && !nr_iowait_cpu(cpu)) {
- ktime_t delta = ktime_sub(now, ts->idle_entrytime);
+ if (ts->idle_active) {
+ ktime_t delta;
+
+ if (ts->idle_active == 2) {
+ ktime_t unused;
+
+ nr_iowait_deltas(cpu, ts->idle_entrytime, now,
+ &unused, &delta);
+ } else {
+ delta = ktime_sub(now, ts->idle_entrytime);
+ }
idle = ktime_add(ts->idle_sleeptime, delta);
} else {
idle = ts->idle_sleeptime;
@@ -510,10 +530,12 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *wall)
do {
seq = read_seqcount_begin(&ts->idle_sleeptime_seq);
-
- if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
- ktime_t delta = ktime_sub(now, ts->idle_entrytime);
+ if (ts->idle_active == 2) {
+ ktime_t delta, unused;
+
+ nr_iowait_deltas(cpu, ts->idle_entrytime, now,
+ &delta, &unused);
iowait = ktime_add(ts->iowait_sleeptime, delta);
} else {
iowait = ts->iowait_sleeptime;
--
1.7.1
--
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