Disable stopping of the idle tick when having live cputime event. When the tick is disabled, the idle counts are out of date until next tick/update and perf cputime PMU provides misleading counts.
Signed-off-by: Jiri Olsa <jo...@kernel.org> --- include/linux/perf_event.h | 1 + kernel/events/cputime.c | 13 +++++++++++++ kernel/time/tick-sched.c | 4 ++++ 3 files changed, 18 insertions(+) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index aa9eaab370be..ba61d2f9602a 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1407,4 +1407,5 @@ int perf_event_exit_cpu(unsigned int cpu); #define perf_event_exit_cpu NULL #endif +bool has_cputime_event(int cpu); #endif /* _LINUX_PERF_EVENT_H */ diff --git a/kernel/events/cputime.c b/kernel/events/cputime.c index efad24543f13..32d3cde0047e 100644 --- a/kernel/events/cputime.c +++ b/kernel/events/cputime.c @@ -1,6 +1,7 @@ #include <linux/kernel_stat.h> #include <linux/sched.h> #include <linux/perf_event.h> +#include <linux/tick.h> enum perf_cputime_id { PERF_CPUTIME_USER, @@ -16,6 +17,13 @@ enum perf_cputime_id { PERF_CPUTIME_MAX, }; +static DEFINE_PER_CPU(int, has_cputime); + +bool has_cputime_event(int cpu) +{ + return per_cpu(has_cputime, cpu) != 0; +} + static enum cpu_usage_stat map[PERF_CPUTIME_MAX] = { [PERF_CPUTIME_USER] = CPUTIME_USER, [PERF_CPUTIME_NICE] = CPUTIME_NICE, @@ -143,12 +151,17 @@ static int cputime_event_add(struct perf_event *event, int flags) if (flags & PERF_EF_START) cputime_event_start(event, flags); + if (event->hw.config == PERF_CPUTIME_IDLE) + tick_nohz_idle_restart_tick(); + + this_cpu_inc(has_cputime); return 0; } static void cputime_event_del(struct perf_event *event, int flags) { cputime_event_stop(event, PERF_EF_UPDATE); + this_cpu_dec(has_cputime); } static void perf_cputime_read(struct perf_event *event) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index da9455a6b42b..1c105bc2a92e 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -28,6 +28,7 @@ #include <linux/posix-timers.h> #include <linux/context_tracking.h> #include <linux/mm.h> +#include <linux/perf_event.h> #include <asm/irq_regs.h> @@ -912,6 +913,9 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) return false; } + if (has_cputime_event(cpu)) + return false; + return true; } -- 2.13.6