From 9d7fb04276481c59610983362d8e023d262b58ca Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 30 Jun 2015 11:30:54 +0200 Subject: sched/cputime: Guarantee stime + utime == rtime While the current code guarantees monotonicity for stime and utime independently of one another, it does not guarantee that the sum of both is equal to the total time we started out with. This confuses things (and peoples) who look at this sum, like top, and will report >100% usage followed by a matching period of 0%. Rework the code to provide both individual monotonicity and a coherent sum. Suggested-by: Fredrik Markstrom Reported-by: Fredrik Markstrom Tested-by: Fredrik Markstrom Signed-off-by: Peter Zijlstra (Intel) Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Rik van Riel Cc: Stanislaw Gruszka Cc: Thomas Gleixner Cc: jason.low2@hp.com Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- include/linux/sched.h | 40 +++++++++++++++++++++++----------------- 1 file changed, 23 insertions(+), 17 deletions(-) (limited to 'include/linux/sched.h') diff --git a/include/linux/sched.h b/include/linux/sched.h index ae21f1591615..7412070a25cc 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -530,39 +530,49 @@ struct cpu_itimer { }; /** - * struct cputime - snaphsot of system and user cputime + * struct prev_cputime - snaphsot of system and user cputime * @utime: time spent in user mode * @stime: time spent in system mode + * @lock: protects the above two fields * - * Gathers a generic snapshot of user and system time. + * Stores previous user/system time values such that we can guarantee + * monotonicity. */ -struct cputime { +struct prev_cputime { +#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE cputime_t utime; cputime_t stime; + raw_spinlock_t lock; +#endif }; +static inline void prev_cputime_init(struct prev_cputime *prev) +{ +#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE + prev->utime = prev->stime = 0; + raw_spin_lock_init(&prev->lock); +#endif +} + /** * struct task_cputime - collected CPU time counts * @utime: time spent in user mode, in &cputime_t units * @stime: time spent in kernel mode, in &cputime_t units * @sum_exec_runtime: total time spent on the CPU, in nanoseconds * - * This is an extension of struct cputime that includes the total runtime - * spent by the task from the scheduler point of view. - * - * As a result, this structure groups together three kinds of CPU time - * that are tracked for threads and thread groups. Most things considering - * CPU time want to group these counts together and treat all three - * of them in parallel. + * This structure groups together three kinds of CPU time that are tracked for + * threads and thread groups. Most things considering CPU time want to group + * these counts together and treat all three of them in parallel. */ struct task_cputime { cputime_t utime; cputime_t stime; unsigned long long sum_exec_runtime; }; + /* Alternate field names when used to cache expirations. */ -#define prof_exp stime #define virt_exp utime +#define prof_exp stime #define sched_exp sum_exec_runtime #define INIT_CPUTIME \ @@ -715,9 +725,7 @@ struct signal_struct { cputime_t utime, stime, cutime, cstime; cputime_t gtime; cputime_t cgtime; -#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE - struct cputime prev_cputime; -#endif + struct prev_cputime prev_cputime; unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw; unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt; unsigned long inblock, oublock, cinblock, coublock; @@ -1481,9 +1489,7 @@ struct task_struct { cputime_t utime, stime, utimescaled, stimescaled; cputime_t gtime; -#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE - struct cputime prev_cputime; -#endif + struct prev_cputime prev_cputime; #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN seqlock_t vtime_seqlock; unsigned long long vtime_snap; -- cgit v1.2.3