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>

1 files changed, 32 insertions, 28 deletions

diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index 535eda7857cf..49aa0a2b0d9e 100644
--- 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));