From a25cac5198d4ff2842ccca63b423962848ad24b2 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 24 Aug 2011 09:40:25 +0200 Subject: proc: Consider NO_HZ when printing idle and iowait times show_stat handler of the /proc/stat file relies on kstat_cpu(cpu) statistics when priting information about idle and iowait times. This is OK if we are not using tickless kernel (CONFIG_NO_HZ) because counters are updated periodically. With NO_HZ things got more tricky because we are not doing idle/iowait accounting while we are tickless so the value might get outdated. Users of /proc/stat will notice that by unchanged idle/iowait values which is then interpreted as 0% idle/iowait time. From the user space POV this is an unexpected behavior and a change of the interface. Let's fix this by using get_cpu_{idle,iowait}_time_us which accounts the total idle/iowait time since boot and it doesn't rely on sampling or any other periodic activity. Fall back to the previous behavior if NO_HZ is disabled or not configured. Signed-off-by: Michal Hocko Cc: Dave Jones Cc: Arnd Bergmann Cc: Alexey Dobriyan Link: http://lkml.kernel.org/r/39181366adac1b39cb6aa3cd53ff0f7c78d32676.1314172057.git.mhocko@suse.cz Signed-off-by: Thomas Gleixner --- fs/proc/stat.c | 41 ++++++++++++++++++++++++++++++++++------- 1 file changed, 34 insertions(+), 7 deletions(-) (limited to 'fs') diff --git a/fs/proc/stat.c b/fs/proc/stat.c index 9758b654a1bc..42b274da92c3 100644 --- a/fs/proc/stat.c +++ b/fs/proc/stat.c @@ -10,6 +10,7 @@ #include #include #include +#include #ifndef arch_irq_stat_cpu #define arch_irq_stat_cpu(cpu) 0 @@ -21,6 +22,35 @@ #define arch_idle_time(cpu) 0 #endif +static cputime64_t get_idle_time(int cpu) +{ + u64 idle_time = get_cpu_idle_time_us(cpu, NULL); + cputime64_t idle; + + if (idle_time == -1ULL) { + /* !NO_HZ so we can rely on cpustat.idle */ + idle = kstat_cpu(cpu).cpustat.idle; + idle = cputime64_add(idle, arch_idle_time(cpu)); + } else + idle = usecs_to_cputime(idle_time); + + return idle; +} + +static cputime64_t get_iowait_time(int cpu) +{ + u64 iowait_time = get_cpu_iowait_time_us(cpu, NULL); + cputime64_t iowait; + + if (iowait_time == -1ULL) + /* !NO_HZ so we can rely on cpustat.iowait */ + iowait = kstat_cpu(cpu).cpustat.iowait; + else + iowait = usecs_to_cputime(iowait_time); + + return iowait; +} + static int show_stat(struct seq_file *p, void *v) { int i, j; @@ -42,9 +72,8 @@ static int show_stat(struct seq_file *p, void *v) user = cputime64_add(user, kstat_cpu(i).cpustat.user); nice = cputime64_add(nice, kstat_cpu(i).cpustat.nice); system = cputime64_add(system, kstat_cpu(i).cpustat.system); - idle = cputime64_add(idle, kstat_cpu(i).cpustat.idle); - idle = cputime64_add(idle, arch_idle_time(i)); - iowait = cputime64_add(iowait, kstat_cpu(i).cpustat.iowait); + idle = cputime64_add(idle, get_idle_time(i)); + iowait = cputime64_add(iowait, get_iowait_time(i)); irq = cputime64_add(irq, kstat_cpu(i).cpustat.irq); softirq = cputime64_add(softirq, kstat_cpu(i).cpustat.softirq); steal = cputime64_add(steal, kstat_cpu(i).cpustat.steal); @@ -76,14 +105,12 @@ static int show_stat(struct seq_file *p, void *v) (unsigned long long)cputime64_to_clock_t(guest), (unsigned long long)cputime64_to_clock_t(guest_nice)); for_each_online_cpu(i) { - /* Copy values here to work around gcc-2.95.3, gcc-2.96 */ user = kstat_cpu(i).cpustat.user; nice = kstat_cpu(i).cpustat.nice; system = kstat_cpu(i).cpustat.system; - idle = kstat_cpu(i).cpustat.idle; - idle = cputime64_add(idle, arch_idle_time(i)); - iowait = kstat_cpu(i).cpustat.iowait; + idle = get_idle_time(i); + iowait = get_iowait_time(i); irq = kstat_cpu(i).cpustat.irq; softirq = kstat_cpu(i).cpustat.softirq; steal = kstat_cpu(i).cpustat.steal; -- cgit v1.2.1