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proc: read kernel cpu stat pointer once
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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

Link: http://lkml.kernel.org/r/20190114195907.GA9680@avx2
Signed-off-by: Alexey Dobriyan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@torvalds
Alexey Dobriyan authored and torvalds committed Mar 6, 2019
1 parent 867aacc commit 5713f35
Showing 1 changed file with 32 additions and 28 deletions.
60 changes: 32 additions & 28 deletions fs/proc/stat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,29 +23,29 @@

#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;
}

#else

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

Expand All @@ -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;

Expand All @@ -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;

Expand All @@ -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);

Expand All @@ -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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