[PATCH 4.9 v2 0/4] Fix softirq time accounting issues on 4.9

[PATCH 4.9 v2 0/4] Fix softirq time accounting issues on 4.9

[Ivan Delalande]

Hi Greg,

This series fixes issues we've seen with softirq time accounting in 4.9:
  - when ksoftirqd is running at 100% on a CPU, none of the values
    reported by /proc/stat for that CPU will change, sometimes for
    dozens of seconds,
  - large deviations in the total number of ticks accumulated over a
    fixed time for a CPU, probably because of the first issue hitting
    for shorter periods.

We found out that something pretty similar had been reported 9 months
ago, see the reference link below. In that discussion, Rabin Vincent had
made a 4.9 specific patch which fixes our first issue, but we were still
seeing some deviation from the total number of ticks (up to 1.7% from
expected, where we had only 0.2% on older kernels), and you had also
asked for a direct backport from the mainline series, if possible.

As mentioned in that thread, a lot of changes (probably 50+) went into
4.11 to remove cputime, but we could get something working with only the
4 attached patches to fix these two issues. Three of these patches apply
without change, and the second one in the series ("sched/cputime:
Convert kcpustat to nsecs") needed a minor change as a cast had been
added in 527b0a76f41d ("sched/cpuacct: Avoid %lld seq_printf warning")
to fix a build warning on s390. I guess we could also include that patch
in this series, let me know if this is the preferred way to handle this.

We ran our tests on 3.18, 4.4 and 4.9 and confirmed that only 4.9 would
need this series, and that this series indeed restores the behavior we
were seeing on those older kernels.

Thanks!

Reference: http://lkml.kernel.org/r/%3C1513159876-5125-1-git-send-email-rabin.vincent@axis.com


v2: - drop "time: Introduce jiffies64_to_nsecs()" as it has already been
      merged into v4.9.132,
    - include backport of commit 564b733c899f ("macintosh/rack-meter:
      Convert cputime64_t use to u64") to avoid introducing a build
      failure on powerpc.


Frederic Weisbecker (4):
  sched/cputime: Convert kcpustat to nsecs
  macintosh/rack-meter: Convert cputime64_t use to u64
  sched/cputime: Increment kcpustat directly on irqtime account
  sched/cputime: Fix ksoftirqd cputime accounting regression

 arch/s390/appldata/appldata_os.c   | 16 +++----
 drivers/cpufreq/cpufreq.c          |  6 +--
 drivers/cpufreq/cpufreq_governor.c |  2 +-
 drivers/cpufreq/cpufreq_stats.c    |  1 -
 drivers/macintosh/rack-meter.c     | 28 +++++------
 fs/proc/stat.c                     | 68 +++++++++++++--------------
 fs/proc/uptime.c                   |  7 +--
 kernel/sched/cpuacct.c             |  2 +-
 kernel/sched/cputime.c             | 75 +++++++++++++-----------------
 kernel/sched/sched.h               | 12 +++--
 10 files changed, 104 insertions(+), 113 deletions(-)

-- 
2.19.1

[PATCH 4.9 v2 1/4] sched/cputime: Convert kcpustat to nsecs

[Ivan Delalande]

From: Frederic Weisbecker <fweisbec@gmail.com>

commit 7fb1327ee9b92fca27662f9b9d60c7c3376d6c69 upstream.

Kernel CPU stats are stored in cputime_t which is an architecture
defined type, and hence a bit opaque and requiring accessors and mutators
for any operation.

Converting them to nsecs simplifies the code and is one step toward
the removal of cputime_t in the core code.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[colona: minor conflict as 527b0a76f41d ("sched/cpuacct: Avoid %lld seq_printf
warning") is missing from v4.9]
Signed-off-by: Ivan Delalande <colona@arista.com>
---
 arch/s390/appldata/appldata_os.c   | 16 +++----
 drivers/cpufreq/cpufreq.c          |  6 +--
 drivers/cpufreq/cpufreq_governor.c |  2 +-
 drivers/cpufreq/cpufreq_stats.c    |  1 -
 drivers/macintosh/rack-meter.c     |  2 +-
 fs/proc/stat.c                     | 68 +++++++++++++++---------------
 fs/proc/uptime.c                   |  7 +--
 kernel/sched/cpuacct.c             |  2 +-
 kernel/sched/cputime.c             | 22 +++++-----
 9 files changed, 61 insertions(+), 65 deletions(-)

diff --git a/arch/s390/appldata/appldata_os.c b/arch/s390/appldata/appldata_os.c
index 69b23b25ac34..08b9e942a262 100644
--- a/arch/s390/appldata/appldata_os.c
+++ b/arch/s390/appldata/appldata_os.c
@@ -113,21 +113,21 @@ static void appldata_get_os_data(void *data)
 	j = 0;
 	for_each_online_cpu(i) {
 		os_data->os_cpu[j].per_cpu_user =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_USER]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_USER]);
 		os_data->os_cpu[j].per_cpu_nice =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_NICE]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_NICE]);
 		os_data->os_cpu[j].per_cpu_system =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM]);
 		os_data->os_cpu[j].per_cpu_idle =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_IDLE]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_IDLE]);
 		os_data->os_cpu[j].per_cpu_irq =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_IRQ]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_IRQ]);
 		os_data->os_cpu[j].per_cpu_softirq =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ]);
 		os_data->os_cpu[j].per_cpu_iowait =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_IOWAIT]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_IOWAIT]);
 		os_data->os_cpu[j].per_cpu_steal =
-			cputime_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_STEAL]);
+			nsecs_to_jiffies(kcpustat_cpu(i).cpustat[CPUTIME_STEAL]);
 		os_data->os_cpu[j].cpu_id = i;
 		j++;
 	}
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index af5eff6835a8..d6d91e8afa9e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -132,7 +132,7 @@ static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
 	u64 cur_wall_time;
 	u64 busy_time;
 
-	cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());
+	cur_wall_time = jiffies64_to_nsecs(get_jiffies_64());
 
 	busy_time = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
 	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];
@@ -143,9 +143,9 @@ static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
 
 	idle_time = cur_wall_time - busy_time;
 	if (wall)
-		*wall = cputime_to_usecs(cur_wall_time);
+		*wall = div_u64(cur_wall_time, NSEC_PER_USEC);
 
-	return cputime_to_usecs(idle_time);
+	return div_u64(idle_time, NSEC_PER_USEC);
 }
 
 u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 642dd0f183a8..38d1a8216084 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -152,7 +152,7 @@ unsigned int dbs_update(struct cpufreq_policy *policy)
 		if (ignore_nice) {
 			u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
 
-			idle_time += cputime_to_usecs(cur_nice - j_cdbs->prev_cpu_nice);
+			idle_time += div_u64(cur_nice - j_cdbs->prev_cpu_nice, NSEC_PER_USEC);
 			j_cdbs->prev_cpu_nice = cur_nice;
 		}
 
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index 06d3abdffd3a..b084708fd113 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -13,7 +13,6 @@
 #include <linux/cpufreq.h>
 #include <linux/module.h>
 #include <linux/slab.h>
-#include <linux/cputime.h>
 
 static DEFINE_SPINLOCK(cpufreq_stats_lock);
 
diff --git a/drivers/macintosh/rack-meter.c b/drivers/macintosh/rack-meter.c
index 25852e399ab2..13b16f34256c 100644
--- a/drivers/macintosh/rack-meter.c
+++ b/drivers/macintosh/rack-meter.c
@@ -91,7 +91,7 @@ static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
 	if (rackmeter_ignore_nice)
 		retval += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];
 
-	return retval;
+	return nsecs_to_cputime64(retval);
 }
 
 static void rackmeter_setup_i2s(struct rackmeter *rm)
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index d700c42b3572..44475a44cbf1 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -21,23 +21,23 @@
 
 #ifdef arch_idle_time
 
-static cputime64_t get_idle_time(int cpu)
+static u64 get_idle_time(int cpu)
 {
-	cputime64_t idle;
+	u64 idle;
 
 	idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE];
 	if (cpu_online(cpu) && !nr_iowait_cpu(cpu))
-		idle += arch_idle_time(cpu);
+		idle += cputime_to_nsecs(arch_idle_time(cpu));
 	return idle;
 }
 
-static cputime64_t get_iowait_time(int cpu)
+static u64 get_iowait_time(int cpu)
 {
-	cputime64_t iowait;
+	u64 iowait;
 
 	iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT];
 	if (cpu_online(cpu) && nr_iowait_cpu(cpu))
-		iowait += arch_idle_time(cpu);
+		iowait += cputime_to_nsecs(arch_idle_time(cpu));
 	return iowait;
 }
 
@@ -45,32 +45,32 @@ static cputime64_t get_iowait_time(int cpu)
 
 static u64 get_idle_time(int cpu)
 {
-	u64 idle, idle_time = -1ULL;
+	u64 idle, idle_usecs = -1ULL;
 
 	if (cpu_online(cpu))
-		idle_time = get_cpu_idle_time_us(cpu, NULL);
+		idle_usecs = get_cpu_idle_time_us(cpu, NULL);
 
-	if (idle_time == -1ULL)
+	if (idle_usecs == -1ULL)
 		/* !NO_HZ or cpu offline so we can rely on cpustat.idle */
 		idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE];
 	else
-		idle = usecs_to_cputime64(idle_time);
+		idle = idle_usecs * NSEC_PER_USEC;
 
 	return idle;
 }
 
 static u64 get_iowait_time(int cpu)
 {
-	u64 iowait, iowait_time = -1ULL;
+	u64 iowait, iowait_usecs = -1ULL;
 
 	if (cpu_online(cpu))
-		iowait_time = get_cpu_iowait_time_us(cpu, NULL);
+		iowait_usecs = get_cpu_iowait_time_us(cpu, NULL);
 
-	if (iowait_time == -1ULL)
+	if (iowait_usecs == -1ULL)
 		/* !NO_HZ or cpu offline so we can rely on cpustat.iowait */
 		iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT];
 	else
-		iowait = usecs_to_cputime64(iowait_time);
+		iowait = iowait_usecs * NSEC_PER_USEC;
 
 	return iowait;
 }
@@ -115,16 +115,16 @@ static int show_stat(struct seq_file *p, void *v)
 	}
 	sum += arch_irq_stat();
 
-	seq_put_decimal_ull(p, "cpu  ", cputime64_to_clock_t(user));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(nice));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(system));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(idle));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(iowait));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(irq));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(softirq));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(steal));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(guest));
-	seq_put_decimal_ull(p, " ", cputime64_to_clock_t(guest_nice));
+	seq_put_decimal_ull(p, "cpu  ", nsec_to_clock_t(user));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(system));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(idle));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(iowait));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(irq));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(softirq));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(steal));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest));
+	seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest_nice));
 	seq_putc(p, '\n');
 
 	for_each_online_cpu(i) {
@@ -140,16 +140,16 @@ static int show_stat(struct seq_file *p, void *v)
 		guest = kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
 		guest_nice = kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
 		seq_printf(p, "cpu%d", i);
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(user));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(nice));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(system));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(idle));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(iowait));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(irq));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(softirq));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(steal));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(guest));
-		seq_put_decimal_ull(p, " ", cputime64_to_clock_t(guest_nice));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(user));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(system));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(idle));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(iowait));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(irq));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(softirq));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(steal));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest));
+		seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest_nice));
 		seq_putc(p, '\n');
 	}
 	seq_put_decimal_ull(p, "intr ", (unsigned long long)sum);
diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c
index 33de567c25af..7981c4ffe787 100644
--- a/fs/proc/uptime.c
+++ b/fs/proc/uptime.c
@@ -5,23 +5,20 @@
 #include <linux/seq_file.h>
 #include <linux/time.h>
 #include <linux/kernel_stat.h>
-#include <linux/cputime.h>
 
 static int uptime_proc_show(struct seq_file *m, void *v)
 {
 	struct timespec uptime;
 	struct timespec idle;
-	u64 idletime;
 	u64 nsec;
 	u32 rem;
 	int i;
 
-	idletime = 0;
+	nsec = 0;
 	for_each_possible_cpu(i)
-		idletime += (__force u64) kcpustat_cpu(i).cpustat[CPUTIME_IDLE];
+		nsec += (__force u64) kcpustat_cpu(i).cpustat[CPUTIME_IDLE];
 
 	get_monotonic_boottime(&uptime);
-	nsec = cputime64_to_jiffies64(idletime) * TICK_NSEC;
 	idle.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem);
 	idle.tv_nsec = rem;
 	seq_printf(m, "%lu.%02lu %lu.%02lu\n",
diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index bc0b309c3f19..4c882791c10c 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -297,7 +297,7 @@ static int cpuacct_stats_show(struct seq_file *sf, void *v)
 	for (stat = 0; stat < CPUACCT_STAT_NSTATS; stat++) {
 		seq_printf(sf, "%s %lld\n",
 			   cpuacct_stat_desc[stat],
-			   cputime64_to_clock_t(val[stat]));
+			   nsec_to_clock_t(val[stat]));
 	}
 
 	return 0;
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 5ebee3164e64..c07f0cfea07e 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -75,9 +75,9 @@ static cputime_t irqtime_account_update(u64 irqtime, int idx, cputime_t maxtime)
 	u64 *cpustat = kcpustat_this_cpu->cpustat;
 	cputime_t irq_cputime;
 
-	irq_cputime = nsecs_to_cputime64(irqtime) - cpustat[idx];
+	irq_cputime = nsecs_to_cputime64(irqtime - cpustat[idx]);
 	irq_cputime = min(irq_cputime, maxtime);
-	cpustat[idx] += irq_cputime;
+	cpustat[idx] += cputime_to_nsecs(irq_cputime);
 
 	return irq_cputime;
 }
@@ -143,7 +143,7 @@ void account_user_time(struct task_struct *p, cputime_t cputime,
 	index = (task_nice(p) > 0) ? CPUTIME_NICE : CPUTIME_USER;
 
 	/* Add user time to cpustat. */
-	task_group_account_field(p, index, (__force u64) cputime);
+	task_group_account_field(p, index, cputime_to_nsecs(cputime));
 
 	/* Account for user time used */
 	acct_account_cputime(p);
@@ -168,11 +168,11 @@ static void account_guest_time(struct task_struct *p, cputime_t cputime,
 
 	/* Add guest time to cpustat. */
 	if (task_nice(p) > 0) {
-		cpustat[CPUTIME_NICE] += (__force u64) cputime;
-		cpustat[CPUTIME_GUEST_NICE] += (__force u64) cputime;
+		cpustat[CPUTIME_NICE] += cputime_to_nsecs(cputime);
+		cpustat[CPUTIME_GUEST_NICE] += cputime_to_nsecs(cputime);
 	} else {
-		cpustat[CPUTIME_USER] += (__force u64) cputime;
-		cpustat[CPUTIME_GUEST] += (__force u64) cputime;
+		cpustat[CPUTIME_USER] += cputime_to_nsecs(cputime);
+		cpustat[CPUTIME_GUEST] += cputime_to_nsecs(cputime);
 	}
 }
 
@@ -193,7 +193,7 @@ void __account_system_time(struct task_struct *p, cputime_t cputime,
 	account_group_system_time(p, cputime);
 
 	/* Add system time to cpustat. */
-	task_group_account_field(p, index, (__force u64) cputime);
+	task_group_account_field(p, index, cputime_to_nsecs(cputime));
 
 	/* Account for system time used */
 	acct_account_cputime(p);
@@ -234,7 +234,7 @@ void account_steal_time(cputime_t cputime)
 {
 	u64 *cpustat = kcpustat_this_cpu->cpustat;
 
-	cpustat[CPUTIME_STEAL] += (__force u64) cputime;
+	cpustat[CPUTIME_STEAL] += cputime_to_nsecs(cputime);
 }
 
 /*
@@ -247,9 +247,9 @@ void account_idle_time(cputime_t cputime)
 	struct rq *rq = this_rq();
 
 	if (atomic_read(&rq->nr_iowait) > 0)
-		cpustat[CPUTIME_IOWAIT] += (__force u64) cputime;
+		cpustat[CPUTIME_IOWAIT] += cputime_to_nsecs(cputime);
 	else
-		cpustat[CPUTIME_IDLE] += (__force u64) cputime;
+		cpustat[CPUTIME_IDLE] += cputime_to_nsecs(cputime);
 }
 
 /*
-- 
2.19.1

[PATCH 4.9 v2 2/4] macintosh/rack-meter: Convert cputime64_t use to u64

[Ivan Delalande]

From: Frederic Weisbecker <fweisbec@gmail.com>

commit 564b733c899f4e12a64946658960fce80cad0b05 upstream.

cputime_t is going to be removed and replaced by nsecs units,
so convert the drivers/macintosh/rack-meter.c use to u64..

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-5-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ivan Delalande <colona@arista.com>
---
 drivers/macintosh/rack-meter.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/drivers/macintosh/rack-meter.c b/drivers/macintosh/rack-meter.c
index 13b16f34256c..c5aba26c604a 100644
--- a/drivers/macintosh/rack-meter.c
+++ b/drivers/macintosh/rack-meter.c
@@ -52,8 +52,8 @@ struct rackmeter_dma {
 struct rackmeter_cpu {
 	struct delayed_work	sniffer;
 	struct rackmeter	*rm;
-	cputime64_t		prev_wall;
-	cputime64_t		prev_idle;
+	u64			prev_wall;
+	u64			prev_idle;
 	int			zero;
 } ____cacheline_aligned;
 
@@ -81,7 +81,7 @@ static int rackmeter_ignore_nice;
 /* This is copied from cpufreq_ondemand, maybe we should put it in
  * a common header somewhere
  */
-static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
+static inline u64 get_cpu_idle_time(unsigned int cpu)
 {
 	u64 retval;
 
@@ -91,7 +91,7 @@ static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
 	if (rackmeter_ignore_nice)
 		retval += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];
 
-	return nsecs_to_cputime64(retval);
+	return retval;
 }
 
 static void rackmeter_setup_i2s(struct rackmeter *rm)
@@ -217,23 +217,23 @@ static void rackmeter_do_timer(struct work_struct *work)
 		container_of(work, struct rackmeter_cpu, sniffer.work);
 	struct rackmeter *rm = rcpu->rm;
 	unsigned int cpu = smp_processor_id();
-	cputime64_t cur_jiffies, total_idle_ticks;
-	unsigned int total_ticks, idle_ticks;
+	u64 cur_nsecs, total_idle_nsecs;
+	u64 total_nsecs, idle_nsecs;
 	int i, offset, load, cumm, pause;
 
-	cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
-	total_ticks = (unsigned int) (cur_jiffies - rcpu->prev_wall);
-	rcpu->prev_wall = cur_jiffies;
+	cur_nsecs = jiffies64_to_nsecs(get_jiffies_64());
+	total_nsecs = cur_nsecs - rcpu->prev_wall;
+	rcpu->prev_wall = cur_nsecs;
 
-	total_idle_ticks = get_cpu_idle_time(cpu);
-	idle_ticks = (unsigned int) (total_idle_ticks - rcpu->prev_idle);
-	idle_ticks = min(idle_ticks, total_ticks);
-	rcpu->prev_idle = total_idle_ticks;
+	total_idle_nsecs = get_cpu_idle_time(cpu);
+	idle_nsecs = total_idle_nsecs - rcpu->prev_idle;
+	idle_nsecs = min(idle_nsecs, total_nsecs);
+	rcpu->prev_idle = total_idle_nsecs;
 
 	/* We do a very dumb calculation to update the LEDs for now,
 	 * we'll do better once we have actual PWM implemented
 	 */
-	load = (9 * (total_ticks - idle_ticks)) / total_ticks;
+	load = div64_u64(9 * (total_nsecs - idle_nsecs), total_nsecs);
 
 	offset = cpu << 3;
 	cumm = 0;
@@ -278,7 +278,7 @@ static void rackmeter_init_cpu_sniffer(struct rackmeter *rm)
 			continue;
 		rcpu = &rm->cpu[cpu];
 		rcpu->prev_idle = get_cpu_idle_time(cpu);
-		rcpu->prev_wall = jiffies64_to_cputime64(get_jiffies_64());
+		rcpu->prev_wall = jiffies64_to_nsecs(get_jiffies_64());
 		schedule_delayed_work_on(cpu, &rm->cpu[cpu].sniffer,
 					 msecs_to_jiffies(CPU_SAMPLING_RATE));
 	}
-- 
2.19.1

[PATCH 4.9 v2 3/4] sched/cputime: Increment kcpustat directly on irqtime account

[Ivan Delalande]

From: Frederic Weisbecker <fweisbec@gmail.com>

commit a499a5a14dbd1d0315a96fc62a8798059325e9e6 upstream.

The irqtime is accounted is nsecs and stored in
cpu_irq_time.hardirq_time and cpu_irq_time.softirq_time. Once the
accumulated amount reaches a new jiffy, this one gets accounted to the
kcpustat.

This was necessary when kcpustat was stored in cputime_t, which could at
worst have jiffies granularity. But now kcpustat is stored in nsecs
so this whole discretization game with temporary irqtime storage has
become unnecessary.

We can now directly account the irqtime to the kcpustat.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-17-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ivan Delalande <colona@arista.com>
---
 kernel/sched/cputime.c | 50 ++++++++++++++----------------------------
 kernel/sched/sched.h   |  7 +++---
 2 files changed, 21 insertions(+), 36 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index c07f0cfea07e..2c2060c99896 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -44,6 +44,7 @@ void disable_sched_clock_irqtime(void)
 void irqtime_account_irq(struct task_struct *curr)
 {
 	struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
+	u64 *cpustat = kcpustat_this_cpu->cpustat;
 	s64 delta;
 	int cpu;
 
@@ -61,49 +62,35 @@ void irqtime_account_irq(struct task_struct *curr)
 	 * in that case, so as not to confuse scheduler with a special task
 	 * that do not consume any time, but still wants to run.
 	 */
-	if (hardirq_count())
-		irqtime->hardirq_time += delta;
-	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
-		irqtime->softirq_time += delta;
+	if (hardirq_count()) {
+		cpustat[CPUTIME_IRQ] += delta;
+		irqtime->tick_delta += delta;
+	} else if (in_serving_softirq() && curr != this_cpu_ksoftirqd()) {
+		cpustat[CPUTIME_SOFTIRQ] += delta;
+		irqtime->tick_delta += delta;
+	}
 
 	u64_stats_update_end(&irqtime->sync);
 }
 EXPORT_SYMBOL_GPL(irqtime_account_irq);
 
-static cputime_t irqtime_account_update(u64 irqtime, int idx, cputime_t maxtime)
+static cputime_t irqtime_tick_accounted(cputime_t maxtime)
 {
-	u64 *cpustat = kcpustat_this_cpu->cpustat;
-	cputime_t irq_cputime;
-
-	irq_cputime = nsecs_to_cputime64(irqtime - cpustat[idx]);
-	irq_cputime = min(irq_cputime, maxtime);
-	cpustat[idx] += cputime_to_nsecs(irq_cputime);
-
-	return irq_cputime;
-}
+	struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
+	cputime_t delta;
 
-static cputime_t irqtime_account_hi_update(cputime_t maxtime)
-{
-	return irqtime_account_update(__this_cpu_read(cpu_irqtime.hardirq_time),
-				      CPUTIME_IRQ, maxtime);
-}
+	delta = nsecs_to_cputime(irqtime->tick_delta);
+	delta = min(delta, maxtime);
+	irqtime->tick_delta -= cputime_to_nsecs(delta);
 
-static cputime_t irqtime_account_si_update(cputime_t maxtime)
-{
-	return irqtime_account_update(__this_cpu_read(cpu_irqtime.softirq_time),
-				      CPUTIME_SOFTIRQ, maxtime);
+	return delta;
 }
 
 #else /* CONFIG_IRQ_TIME_ACCOUNTING */
 
 #define sched_clock_irqtime	(0)
 
-static cputime_t irqtime_account_hi_update(cputime_t dummy)
-{
-	return 0;
-}
-
-static cputime_t irqtime_account_si_update(cputime_t dummy)
+static cputime_t irqtime_tick_accounted(cputime_t dummy)
 {
 	return 0;
 }
@@ -290,10 +277,7 @@ static inline cputime_t account_other_time(cputime_t max)
 	accounted = steal_account_process_time(max);
 
 	if (accounted < max)
-		accounted += irqtime_account_hi_update(max - accounted);
-
-	if (accounted < max)
-		accounted += irqtime_account_si_update(max - accounted);
+		accounted += irqtime_tick_accounted(max - accounted);
 
 	return accounted;
 }
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index f564a1d2c9d5..187c556196af 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -4,6 +4,7 @@
 #include <linux/sched/rt.h>
 #include <linux/u64_stats_sync.h>
 #include <linux/sched/deadline.h>
+#include <linux/kernel_stat.h>
 #include <linux/binfmts.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
@@ -1742,8 +1743,7 @@ static inline void nohz_balance_exit_idle(unsigned int cpu) { }
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 struct irqtime {
-	u64			hardirq_time;
-	u64			softirq_time;
+	u64			tick_delta;
 	u64			irq_start_time;
 	struct u64_stats_sync	sync;
 };
@@ -1753,12 +1753,13 @@ DECLARE_PER_CPU(struct irqtime, cpu_irqtime);
 static inline u64 irq_time_read(int cpu)
 {
 	struct irqtime *irqtime = &per_cpu(cpu_irqtime, cpu);
+	u64 *cpustat = kcpustat_cpu(cpu).cpustat;
 	unsigned int seq;
 	u64 total;
 
 	do {
 		seq = __u64_stats_fetch_begin(&irqtime->sync);
-		total = irqtime->softirq_time + irqtime->hardirq_time;
+		total = cpustat[CPUTIME_SOFTIRQ] + cpustat[CPUTIME_IRQ];
 	} while (__u64_stats_fetch_retry(&irqtime->sync, seq));
 
 	return total;
-- 
2.19.1

[PATCH 4.9 v2 4/4] sched/cputime: Fix ksoftirqd cputime accounting regression

[Ivan Delalande]

From: Frederic Weisbecker <fweisbec@gmail.com>

commit 25e2d8c1b9e327ed260edd13169cc22bc7a78bc6 upstream.

irq_time_read() returns the irqtime minus the ksoftirqd time. This
is necessary because irq_time_read() is used to substract the IRQ time
from the sum_exec_runtime of a task. If we were to include the softirq
time of ksoftirqd, this task would substract its own CPU time everytime
it updates ksoftirqd->sum_exec_runtime which would therefore never
progress.

But this behaviour got broken by:

  a499a5a14db ("sched/cputime: Increment kcpustat directly on irqtime account")

... which now includes ksoftirqd softirq time in the time returned by
irq_time_read().

This has resulted in wrong ksoftirqd cputime reported to userspace
through /proc/stat and thus "top" not showing ksoftirqd when it should
after intense networking load.

ksoftirqd->stime happens to be correct but it gets scaled down by
sum_exec_runtime through task_cputime_adjusted().

To fix this, just account the strict IRQ time in a separate counter and
use it to report the IRQ time.

Reported-and-tested-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1493129448-5356-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ivan Delalande <colona@arista.com>
---
 kernel/sched/cputime.c | 27 ++++++++++++++++-----------
 kernel/sched/sched.h   |  9 +++++++--
 2 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 2c2060c99896..448d6426fa5f 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -37,6 +37,18 @@ void disable_sched_clock_irqtime(void)
 	sched_clock_irqtime = 0;
 }
 
+static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
+				  enum cpu_usage_stat idx)
+{
+	u64 *cpustat = kcpustat_this_cpu->cpustat;
+
+	u64_stats_update_begin(&irqtime->sync);
+	cpustat[idx] += delta;
+	irqtime->total += delta;
+	irqtime->tick_delta += delta;
+	u64_stats_update_end(&irqtime->sync);
+}
+
 /*
  * Called before incrementing preempt_count on {soft,}irq_enter
  * and before decrementing preempt_count on {soft,}irq_exit.
@@ -44,7 +56,6 @@ void disable_sched_clock_irqtime(void)
 void irqtime_account_irq(struct task_struct *curr)
 {
 	struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
-	u64 *cpustat = kcpustat_this_cpu->cpustat;
 	s64 delta;
 	int cpu;
 
@@ -55,22 +66,16 @@ void irqtime_account_irq(struct task_struct *curr)
 	delta = sched_clock_cpu(cpu) - irqtime->irq_start_time;
 	irqtime->irq_start_time += delta;
 
-	u64_stats_update_begin(&irqtime->sync);
 	/*
 	 * We do not account for softirq time from ksoftirqd here.
 	 * We want to continue accounting softirq time to ksoftirqd thread
 	 * in that case, so as not to confuse scheduler with a special task
 	 * that do not consume any time, but still wants to run.
 	 */
-	if (hardirq_count()) {
-		cpustat[CPUTIME_IRQ] += delta;
-		irqtime->tick_delta += delta;
-	} else if (in_serving_softirq() && curr != this_cpu_ksoftirqd()) {
-		cpustat[CPUTIME_SOFTIRQ] += delta;
-		irqtime->tick_delta += delta;
-	}
-
-	u64_stats_update_end(&irqtime->sync);
+	if (hardirq_count())
+		irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
+	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
+		irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
 }
 EXPORT_SYMBOL_GPL(irqtime_account_irq);
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 187c556196af..923cc35e8490 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1743,6 +1743,7 @@ static inline void nohz_balance_exit_idle(unsigned int cpu) { }
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 struct irqtime {
+	u64			total;
 	u64			tick_delta;
 	u64			irq_start_time;
 	struct u64_stats_sync	sync;
@@ -1750,16 +1751,20 @@ struct irqtime {
 
 DECLARE_PER_CPU(struct irqtime, cpu_irqtime);
 
+/*
+ * Returns the irqtime minus the softirq time computed by ksoftirqd.
+ * Otherwise ksoftirqd's sum_exec_runtime is substracted its own runtime
+ * and never move forward.
+ */
 static inline u64 irq_time_read(int cpu)
 {
 	struct irqtime *irqtime = &per_cpu(cpu_irqtime, cpu);
-	u64 *cpustat = kcpustat_cpu(cpu).cpustat;
 	unsigned int seq;
 	u64 total;
 
 	do {
 		seq = __u64_stats_fetch_begin(&irqtime->sync);
-		total = cpustat[CPUTIME_SOFTIRQ] + cpustat[CPUTIME_IRQ];
+		total = irqtime->total;
 	} while (__u64_stats_fetch_retry(&irqtime->sync, seq));
 
 	return total;
-- 
2.19.1

Re: [PATCH 4.9 v2 0/4] Fix softirq time accounting issues on 4.9

[Greg Kroah-Hartman]

On Fri, Oct 12, 2018 at 07:10:55PM -0700, Ivan Delalande wrote:
> Hi Greg,
> 
> This series fixes issues we've seen with softirq time accounting in 4.9:
>   - when ksoftirqd is running at 100% on a CPU, none of the values
>     reported by /proc/stat for that CPU will change, sometimes for
>     dozens of seconds,
>   - large deviations in the total number of ticks accumulated over a
>     fixed time for a CPU, probably because of the first issue hitting
>     for shorter periods.
> 
> We found out that something pretty similar had been reported 9 months
> ago, see the reference link below. In that discussion, Rabin Vincent had
> made a 4.9 specific patch which fixes our first issue, but we were still
> seeing some deviation from the total number of ticks (up to 1.7% from
> expected, where we had only 0.2% on older kernels), and you had also
> asked for a direct backport from the mainline series, if possible.
> 
> As mentioned in that thread, a lot of changes (probably 50+) went into
> 4.11 to remove cputime, but we could get something working with only the
> 4 attached patches to fix these two issues. Three of these patches apply
> without change, and the second one in the series ("sched/cputime:
> Convert kcpustat to nsecs") needed a minor change as a cast had been
> added in 527b0a76f41d ("sched/cpuacct: Avoid %lld seq_printf warning")
> to fix a build warning on s390. I guess we could also include that patch
> in this series, let me know if this is the preferred way to handle this.
> 
> We ran our tests on 3.18, 4.4 and 4.9 and confirmed that only 4.9 would
> need this series, and that this series indeed restores the behavior we
> were seeing on those older kernels.
> 
> Thanks!
> 
> Reference: http://lkml.kernel.org/r/%3C1513159876-5125-1-git-send-email-rabin.vincent@axis.com
> 
> 
> v2: - drop "time: Introduce jiffies64_to_nsecs()" as it has already been
>       merged into v4.9.132,
>     - include backport of commit 564b733c899f ("macintosh/rack-meter:
>       Convert cputime64_t use to u64") to avoid introducing a build
>       failure on powerpc.

Ok, let's try this again, all queued up.

greg k-h