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Subject[PATCH] proc: read kernel cpu stat pointer once
Help gcc generate better code:

$ ./scripts/bloat-o-meter ../vmlinux-000 ../vmlinux-001
add/remove: 2/2 grow/shrink: 0/1 up/down: 92/-142 (-50)
Function old new delta
get_iowait_time.isra - 46 +46
get_idle_time.isra - 46 +46
show_stat 1489 1477 -12
get_iowait_time 65 - -65
get_idle_time 65 - -65

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

fs/proc/stat.c | 60 ++++++++++++++++++++++++++++++---------------------------
1 file changed, 32 insertions(+), 28 deletions(-)

--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -23,21 +23,21 @@

#ifdef arch_idle_time

-static u64 get_idle_time(int cpu)
+static u64 get_idle_time(struct kernel_cpustat *kcs, int cpu)
{
u64 idle;

- idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE];
+ idle = kcs->cpustat[CPUTIME_IDLE];
if (cpu_online(cpu) && !nr_iowait_cpu(cpu))
idle += arch_idle_time(cpu);
return idle;
}

-static u64 get_iowait_time(int cpu)
+static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu)
{
u64 iowait;

- iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT];
+ iowait = kcs->cpustat[CPUTIME_IOWAIT];
if (cpu_online(cpu) && nr_iowait_cpu(cpu))
iowait += arch_idle_time(cpu);
return iowait;
@@ -45,7 +45,7 @@ static u64 get_iowait_time(int cpu)

#else

-static u64 get_idle_time(int cpu)
+static u64 get_idle_time(struct kernel_cpustat *kcs, int cpu)
{
u64 idle, idle_usecs = -1ULL;

@@ -54,14 +54,14 @@ static u64 get_idle_time(int cpu)

if (idle_usecs == -1ULL)
/* !NO_HZ or cpu offline so we can rely on cpustat.idle */
- idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE];
+ idle = kcs->cpustat[CPUTIME_IDLE];
else
idle = idle_usecs * NSEC_PER_USEC;

return idle;
}

-static u64 get_iowait_time(int cpu)
+static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu)
{
u64 iowait, iowait_usecs = -1ULL;

@@ -70,7 +70,7 @@ static u64 get_iowait_time(int cpu)

if (iowait_usecs == -1ULL)
/* !NO_HZ or cpu offline so we can rely on cpustat.iowait */
- iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT];
+ iowait = kcs->cpustat[CPUTIME_IOWAIT];
else
iowait = iowait_usecs * NSEC_PER_USEC;

@@ -95,16 +95,18 @@ static int show_stat(struct seq_file *p, void *v)
getboottime64(&boottime);

for_each_possible_cpu(i) {
- user += kcpustat_cpu(i).cpustat[CPUTIME_USER];
- nice += kcpustat_cpu(i).cpustat[CPUTIME_NICE];
- system += kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM];
- idle += get_idle_time(i);
- iowait += get_iowait_time(i);
- irq += kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
- softirq += kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ];
- steal += kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
- guest += kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
- guest_nice += kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
+ struct kernel_cpustat *kcs = &kcpustat_cpu(i);
+
+ user += kcs->cpustat[CPUTIME_USER];
+ nice += kcs->cpustat[CPUTIME_NICE];
+ system += kcs->cpustat[CPUTIME_SYSTEM];
+ idle += get_idle_time(kcs, i);
+ iowait += get_iowait_time(kcs, i);
+ irq += kcs->cpustat[CPUTIME_IRQ];
+ softirq += kcs->cpustat[CPUTIME_SOFTIRQ];
+ steal += kcs->cpustat[CPUTIME_STEAL];
+ guest += kcs->cpustat[CPUTIME_GUEST];
+ guest_nice += kcs->cpustat[CPUTIME_GUEST_NICE];
sum += kstat_cpu_irqs_sum(i);
sum += arch_irq_stat_cpu(i);

@@ -130,17 +132,19 @@ static int show_stat(struct seq_file *p, void *v)
seq_putc(p, '\n');

for_each_online_cpu(i) {
+ struct kernel_cpustat *kcs = &kcpustat_cpu(i);
+
/* Copy values here to work around gcc-2.95.3, gcc-2.96 */
- user = kcpustat_cpu(i).cpustat[CPUTIME_USER];
- nice = kcpustat_cpu(i).cpustat[CPUTIME_NICE];
- system = kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM];
- idle = get_idle_time(i);
- iowait = get_iowait_time(i);
- irq = kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
- softirq = kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ];
- steal = kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
- guest = kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
- guest_nice = kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
+ user = kcs->cpustat[CPUTIME_USER];
+ nice = kcs->cpustat[CPUTIME_NICE];
+ system = kcs->cpustat[CPUTIME_SYSTEM];
+ idle = get_idle_time(kcs, i);
+ iowait = get_iowait_time(kcs, i);
+ irq = kcs->cpustat[CPUTIME_IRQ];
+ softirq = kcs->cpustat[CPUTIME_SOFTIRQ];
+ steal = kcs->cpustat[CPUTIME_STEAL];
+ guest = kcs->cpustat[CPUTIME_GUEST];
+ guest_nice = kcs->cpustat[CPUTIME_GUEST_NICE];
seq_printf(p, "cpu%d", i);
seq_put_decimal_ull(p, " ", nsec_to_clock_t(user));
seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));
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