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

Link: http://lkml.kernel.org/r/20190114195907.GA9680@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index 535eda7..49aa0a2 100644 (file)
--- 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));