[PATCH v11 01/12] sched/cputime: Add kcpustat_field_total helper

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Provide a new helper function which sums up a given type of cpustat
over a specified cpumask.

This allows the caller's code to be simpler and avoids duplication.
For example, subsequent patch in the steal governor use this exact
same pattern when calculating steal time.

Suggested-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Yury Norov <ynorov@nvidia.com>
Reviewed-by: Mete Durlu <meted@linux.ibm.com>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 arch/s390/kernel/hiperdispatch.c | 10 +++-------
 fs/proc/uptime.c                 |  6 +-----
 include/linux/kernel_stat.h      | 11 +++++++++++
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/arch/s390/kernel/hiperdispatch.c b/arch/s390/kernel/hiperdispatch.c
index 217206522266..c21496f0a141 100644
--- a/arch/s390/kernel/hiperdispatch.c
+++ b/arch/s390/kernel/hiperdispatch.c
@@ -207,16 +207,12 @@ static unsigned long hd_calculate_steal_percentage(void)
 {
 	unsigned long time_delta, steal_delta, steal, percentage;
 	static ktime_t prev;
-	int cpus, cpu;
+	int cpus;
 	ktime_t now;
 
-	cpus = 0;
-	steal = 0;
 	percentage = 0;
-	for_each_cpu(cpu, &hd_vmvl_cpumask) {
-		steal += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
-		cpus++;
-	}
+	steal = kcpustat_field_total(CPUTIME_STEAL, &hd_vmvl_cpumask);
+	cpus = cpumask_weight(&hd_vmvl_cpumask);
 	/*
 	 * If there is no vertical medium and low CPUs steal time
 	 * is 0 as vertical high CPUs shouldn't experience steal time.
diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c
index 433aa947cd57..53143c66cbe1 100644
--- a/fs/proc/uptime.c
+++ b/fs/proc/uptime.c
@@ -15,12 +15,8 @@ static int uptime_proc_show(struct seq_file *m, void *v)
 	struct timespec64 idle;
 	u64 idle_nsec;
 	u32 rem;
-	int i;
-
-	idle_nsec = 0;
-	for_each_possible_cpu(i)
-		idle_nsec += kcpustat_field(CPUTIME_IDLE, i);
 
+	idle_nsec = kcpustat_field_total(CPUTIME_IDLE, cpu_possible_mask);
 	ktime_get_boottime_ts64(&uptime);
 	timens_add_boottime(&uptime);
 
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 9ca6c2259dfe..c1e85550bf12 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -196,6 +196,17 @@ static inline void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu)
 }
 #endif /* !CONFIG_VIRT_CPU_ACCOUNTING_GEN */
 
+static inline u64 kcpustat_field_total(enum cpu_usage_stat usage, const struct cpumask *cpus)
+{
+	u64 total = 0;
+	int cpu;
+
+	for_each_cpu(cpu, cpus)
+		total += kcpustat_field(usage, cpu);
+
+	return total;
+}
+
 extern void account_user_time(struct task_struct *, u64);
 extern void account_guest_time(struct task_struct *, u64);
 extern void account_system_time(struct task_struct *, int, u64);
-- 
2.47.3