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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/sched.h | |
| parent | 3f5ad91488e813026f8c5f46b839e91a83912703 (diff) | |
| download | lwn-c006fac556e401a62054d065da168099ea5a5b10.tar.gz lwn-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/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index bde72482cbb8..a189bec13729 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -58,6 +58,7 @@ #include <linux/prefetch.h> #include <linux/profile.h> #include <linux/psi.h> +#include <linux/ratelimit.h> #include <linux/rcupdate_wait.h> #include <linux/security.h> #include <linux/stop_machine.h> @@ -971,6 +972,11 @@ struct rq { atomic_t nr_iowait; +#ifdef CONFIG_SCHED_DEBUG + u64 last_seen_need_resched_ns; + int ticks_without_resched; +#endif + #ifdef CONFIG_MEMBARRIER int membarrier_state; #endif @@ -2371,6 +2377,8 @@ extern void print_dl_stats(struct seq_file *m, int cpu); extern void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq); extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq); extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq); + +extern void resched_latency_warn(int cpu, u64 latency); #ifdef CONFIG_NUMA_BALANCING extern void show_numa_stats(struct task_struct *p, struct seq_file *m); @@ -2378,6 +2386,8 @@ extern void print_numa_stats(struct seq_file *m, int node, unsigned long tsf, unsigned long tpf, unsigned long gsf, unsigned long gpf); #endif /* CONFIG_NUMA_BALANCING */ +#else +static inline void resched_latency_warn(int cpu, u64 latency) {} #endif /* CONFIG_SCHED_DEBUG */ extern void init_cfs_rq(struct cfs_rq *cfs_rq); |