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| author |   Paul Turner <pjt@google.com> | 2021-04-16 14:29:36 -0700 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2021-04-21 13:55:41 +0200 |
| commit | c006fac556e401a62054d065da168099ea5a5b10 (patch) | |
| tree | d35910fa4eab4ab7821226ebc76709a04a33baf5 /kernel/sched/debug.c | |
| parent | sched/fair: Move update_nohz_stats() to the CONFIG_NO_HZ_COMMON block to simplify the code & fix an unused function warning (diff) | |
| download | linux-dev-c006fac556e401a62054d065da168099ea5a5b10.tar.xz linux-dev-c006fac556e401a62054d065da168099ea5a5b10.zip | |
sched: Warn on long periods of pending need_resched
CPU scheduler marks need_resched flag to signal a schedule() on a
particular CPU. But, schedule() may not happen immediately in cases
where the current task is executing in the kernel mode (no
preemption state) for extended periods of time.
This patch adds a warn_on if need_resched is pending for more than the
time specified in sysctl resched_latency_warn_ms. If it goes off, it is
likely that there is a missing cond_resched() somewhere. Monitoring is
done via the tick and the accuracy is hence limited to jiffy scale. This
also means that we won't trigger the warning if the tick is disabled.
This feature (LATENCY_WARN) is default disabled.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210416212936.390566-1-joshdon@google.com
Diffstat (limited to 'kernel/sched/debug.c')
| -rw-r--r-- | kernel/sched/debug.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 461342f598ef..7251fc477a11 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -309,6 +309,9 @@ static __init int sched_init_debug(void) debugfs_create_u32("min_granularity_ns", 0644, debugfs_sched, &sysctl_sched_min_granularity); debugfs_create_u32("wakeup_granularity_ns", 0644, debugfs_sched, &sysctl_sched_wakeup_granularity); + debugfs_create_u32("latency_warn_ms", 0644, debugfs_sched, &sysctl_resched_latency_warn_ms); + debugfs_create_u32("latency_warn_once", 0644, debugfs_sched, &sysctl_resched_latency_warn_once); + #ifdef CONFIG_SMP debugfs_create_file("tunable_scaling", 0644, debugfs_sched, NULL, &sched_scaling_fops); debugfs_create_u32("migration_cost_ns", 0644, debugfs_sched, &sysctl_sched_migration_cost); @@ -1027,3 +1030,13 @@ void proc_sched_set_task(struct task_struct *p) memset(&p->se.statistics, 0, sizeof(p->se.statistics)); #endif } + +void resched_latency_warn(int cpu, u64 latency) +{ + static DEFINE_RATELIMIT_STATE(latency_check_ratelimit, 60 * 60 * HZ, 1); + + WARN(__ratelimit(&latency_check_ratelimit), + "sched: CPU %d need_resched set for > %llu ns (%d ticks) " + "without schedule\n", + cpu, latency, cpu_rq(cpu)->ticks_without_resched); +} |