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Commit 556f086b authored by Joonwoo Park's avatar Joonwoo Park
Browse files

Revert "sched: warn/panic upon excessive scheduling latency" 



This reverts commit ab9e1373 ("sched: warn/panic upon excessive
scheduling latency") as this feature is no longer used.

Change-Id: Ibf7d8340b87f6772a42e6edb22f9f3cd73e05512
Signed-off-by: default avatarJoonwoo Park <joonwoop@codeaurora.org>
parent ef07180f

Documentation/scheduler/sched-stats.txt

+0 −9
Original line number Diff line number Diff line
@@ -147,15 +147,6 @@ this file correlating for that process to: 
     2) time spent waiting on a runqueue

     3) # of timeslices run on this cpu



/proc/sys/kernel/{sched_latency_warn_threshold_us,sched_latency_panic_threshold_us}

----------------

schedstats provides procfs nodes /proc/sys/kernel/sched_latency_warn_threshold_us

and /proc/sys/kernel/sched_latency_panic_threshold_us.  These can be configured

to detect unreasonably high scheduling latency.

Set sched_latency_warn_threshold_us or sched_latency_panic_threshold_us with

non-zero threshold to warn or panic system when scheduling latency higher than

configured threshold is detected.  Default is 0 (disabled) for both.



A program could be easily written to make use of these extra fields to

report on how well a particular process or set of processes is faring

under the scheduler's policies.  A simple version of such a program is

include/linux/sched/sysctl.h

+1 −1
Original line number Diff line number Diff line
@@ -159,9 +159,9 @@ extern unsigned int sysctl_sched_autogroup_enabled; 
#endif



#ifdef CONFIG_SCHEDSTATS

#ifdef CONFIG_SCHED_QHMP

extern unsigned int sysctl_sched_latency_panic_threshold;

extern unsigned int sysctl_sched_latency_warn_threshold;

#ifdef CONFIG_SCHED_QHMP

extern int sched_max_latency_sysctl(struct ctl_table *table, int write,

				    void __user *buffer, size_t *lenp,

				    loff_t *ppos);

kernel/sched/fair.c

+2 −38
Original line number Diff line number Diff line
@@ -30,7 +30,6 @@ 
#include <linux/mempolicy.h>

#include <linux/migrate.h>

#include <linux/task_work.h>

#include <linux/ratelimit.h>



#include "sched.h"

#include <trace/events/sched.h>
@@ -122,11 +121,6 @@ unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; 
unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;

#endif



#ifdef CONFIG_SCHEDSTATS

unsigned int sysctl_sched_latency_panic_threshold;

unsigned int sysctl_sched_latency_warn_threshold;

#endif /* CONFIG_SCHEDSTATS */



static inline void update_load_add(struct load_weight *lw, unsigned long inc)

{

	lw->weight += inc;
@@ -772,31 +766,6 @@ static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, 
		update_stats_wait_start(cfs_rq, se, migrating);

}



#ifdef CONFIG_SCHEDSTATS

static inline void check_for_high_latency(struct task_struct *p, u64 latency_us)

{

	int do_warn, do_panic;

	const char *fmt = "excessive latency comm=%s pid=%d latency=%llu(us)\n";

	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,

				      DEFAULT_RATELIMIT_BURST);



	do_warn = (sysctl_sched_latency_warn_threshold &&

		   latency_us > sysctl_sched_latency_warn_threshold);

	do_panic = (sysctl_sched_latency_panic_threshold &&

		    latency_us > sysctl_sched_latency_panic_threshold);

	if (unlikely(do_panic || (do_warn && __ratelimit(&rs)))) {

		if (do_panic)

			panic(fmt, p->comm, p->pid, latency_us);

		else

			printk_deferred(fmt, p->comm, p->pid, latency_us);

	}

}

#else

static inline void check_for_high_latency(struct task_struct *p, u64 latency)

{

}

#endif



static void

update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se,

		      bool migrating)
@@ -815,13 +784,8 @@ update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se, 
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);

#ifdef CONFIG_SCHEDSTATS

	if (entity_is_task(se)) {

		u64 delta;



		delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;

		trace_sched_stat_wait(task_of(se), delta);



		delta = delta >> 10;

		check_for_high_latency(task_of(se), delta);

		trace_sched_stat_wait(task_of(se),

			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);

	}

#endif

	schedstat_set(se->statistics.wait_start, 0);

kernel/sysctl.c

+1 −1
Original line number Diff line number Diff line
@@ -689,6 +689,7 @@ static struct ctl_table kern_table[] = { 
	},

#endif

#ifdef CONFIG_SCHEDSTATS

#ifdef CONFIG_SCHED_QHMP

	{

		.procname	= "sched_latency_panic_threshold_us",

		.data		= &sysctl_sched_latency_panic_threshold,
@@ -703,7 +704,6 @@ static struct ctl_table kern_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

	},

#ifdef CONFIG_SCHED_QHMP

	{

		.procname	= "sched_max_latency_us",

		.mode		= 0644,