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Commit 42ab5394 authored by Joonwoo Park's avatar Joonwoo Park Committed by Kyle Yan
Browse files

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



This reverts commit 8f90803a ("sched: warn/panic upon excessive
scheduling latency") as this feature is no longer used.

Change-Id: I200d0e9e8dad5047522cd02a68de25d4a70a91a4
Signed-off-by: default avatarJoonwoo Park <joonwoop@codeaurora.org>
parent 9103cfba

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

+0 −5
Original line number Diff line number Diff line
@@ -131,11 +131,6 @@ extern unsigned int sysctl_sched_cfs_bandwidth_slice; 
extern unsigned int sysctl_sched_autogroup_enabled;

#endif



#ifdef CONFIG_SCHEDSTATS

extern unsigned int sysctl_sched_latency_panic_threshold;

extern unsigned int sysctl_sched_latency_warn_threshold;

#endif



extern int sched_rr_timeslice;



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

kernel/sched/fair.c

+0 −26
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;
@@ -755,25 +749,6 @@ static void update_curr_fair(struct rq *rq) 
}



#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);

	}

}



static inline void

update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)

{
@@ -804,7 +779,6 @@ update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) 
			return;

		}

		trace_sched_stat_wait(p, delta);

		check_for_high_latency(p, delta >> 10);

	}



	se->statistics.wait_max = max(se->statistics.wait_max, delta);

kernel/sysctl.c

+0 −16
Original line number Diff line number Diff line
@@ -596,22 +596,6 @@ static struct ctl_table kern_table[] = { 
		.extra1		= &one,

	},

#endif

#ifdef CONFIG_SCHEDSTATS

	{

		.procname	= "sched_latency_panic_threshold_us",

		.data		= &sysctl_sched_latency_panic_threshold,

		.maxlen		= sizeof(unsigned int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

	},

	{

		.procname	= "sched_latency_warn_threshold_us",

		.data		= &sysctl_sched_latency_warn_threshold,

		.maxlen		= sizeof(unsigned int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

	},

#endif

#ifdef CONFIG_PROVE_LOCKING

	{

		.procname	= "prove_locking",