From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: 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@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/stat.c | 60 +++++++++++++++++++++++++---------------------- 1 file changed, 32 insertions(+), 28 deletions(-) --- a/fs/proc/stat.c~proc-read-kernel-cpu-stat-pointer-once +++ a/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, 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, 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)); _
