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sched: debug, improve migration statistics
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add new migration statistics when SCHED_DEBUG and SCHEDSTATS
is enabled. Available in /proc/<PID>/sched.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Ingo Molnar committed Oct 15, 2007
1 parent 2d92f22 commit cc36773
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Showing 3 changed files with 149 additions and 32 deletions.
18 changes: 18 additions & 0 deletions include/linux/sched.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -931,6 +931,24 @@ struct sched_entity {
u64 block_max;
u64 exec_max;
u64 slice_max;

u64 nr_migrations;
u64 nr_migrations_cold;
u64 nr_failed_migrations_affine;
u64 nr_failed_migrations_running;
u64 nr_failed_migrations_hot;
u64 nr_forced_migrations;
u64 nr_forced2_migrations;

u64 nr_wakeups;
u64 nr_wakeups_sync;
u64 nr_wakeups_migrate;
u64 nr_wakeups_local;
u64 nr_wakeups_remote;
u64 nr_wakeups_affine;
u64 nr_wakeups_affine_attempts;
u64 nr_wakeups_passive;
u64 nr_wakeups_idle;
#endif

#ifdef CONFIG_FAIR_GROUP_SCHED
Expand Down
76 changes: 54 additions & 22 deletions kernel/sched.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1005,6 +1005,23 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)

#ifdef CONFIG_SMP

/*
* Is this task likely cache-hot:
*/
static inline int
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
{
s64 delta;

if (p->sched_class != &fair_sched_class)
return 0;

delta = now - p->se.exec_start;

return delta < (s64)sysctl_sched_migration_cost;
}


void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
int old_cpu = task_cpu(p);
Expand All @@ -1022,6 +1039,11 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
p->se.sleep_start -= clock_offset;
if (p->se.block_start)
p->se.block_start -= clock_offset;
if (old_cpu != new_cpu) {
schedstat_inc(p, se.nr_migrations);
if (task_hot(p, old_rq->clock, NULL))
schedstat_inc(p, se.nr_forced2_migrations);
}
#endif
p->se.vruntime -= old_cfsrq->min_vruntime -
new_cfsrq->min_vruntime;
Expand Down Expand Up @@ -1394,8 +1416,13 @@ static int wake_idle(int cpu, struct task_struct *p)
if (sd->flags & SD_WAKE_IDLE) {
cpus_and(tmp, sd->span, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
if (idle_cpu(i))
if (idle_cpu(i)) {
if (i != task_cpu(p)) {
schedstat_inc(p,
se.nr_wakeups_idle);
}
return i;
}
}
} else {
break;
Expand Down Expand Up @@ -1426,7 +1453,7 @@ static inline int wake_idle(int cpu, struct task_struct *p)
*/
static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
{
int cpu, this_cpu, success = 0;
int cpu, orig_cpu, this_cpu, success = 0;
unsigned long flags;
long old_state;
struct rq *rq;
Expand All @@ -1445,6 +1472,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
goto out_running;

cpu = task_cpu(p);
orig_cpu = cpu;
this_cpu = smp_processor_id();

#ifdef CONFIG_SMP
Expand Down Expand Up @@ -1488,6 +1516,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
unsigned long tl = this_load;
unsigned long tl_per_task;

schedstat_inc(p, se.nr_wakeups_affine_attempts);
tl_per_task = cpu_avg_load_per_task(this_cpu);

/*
Expand All @@ -1507,6 +1536,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
* there is no bad imbalance.
*/
schedstat_inc(this_sd, ttwu_move_affine);
schedstat_inc(p, se.nr_wakeups_affine);
goto out_set_cpu;
}
}
Expand All @@ -1518,6 +1548,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
if (this_sd->flags & SD_WAKE_BALANCE) {
if (imbalance*this_load <= 100*load) {
schedstat_inc(this_sd, ttwu_move_balance);
schedstat_inc(p, se.nr_wakeups_passive);
goto out_set_cpu;
}
}
Expand All @@ -1543,6 +1574,15 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)

out_activate:
#endif /* CONFIG_SMP */
schedstat_inc(p, se.nr_wakeups);
if (sync)
schedstat_inc(p, se.nr_wakeups_sync);
if (orig_cpu != cpu)
schedstat_inc(p, se.nr_wakeups_migrate);
if (cpu == this_cpu)
schedstat_inc(p, se.nr_wakeups_local);
else
schedstat_inc(p, se.nr_wakeups_remote);
update_rq_clock(rq);
activate_task(rq, p, 1);
/*
Expand Down Expand Up @@ -2118,22 +2158,6 @@ static void pull_task(struct rq *src_rq, struct task_struct *p,
check_preempt_curr(this_rq, p);
}

/*
* Is this task likely cache-hot:
*/
static inline int
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
{
s64 delta;

if (p->sched_class != &fair_sched_class)
return 0;

delta = now - p->se.exec_start;

return delta < (s64)sysctl_sched_migration_cost;
}

/*
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
*/
Expand All @@ -2148,12 +2172,16 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
* 2) cannot be migrated to this CPU due to cpus_allowed, or
* 3) are cache-hot on their current CPU.
*/
if (!cpu_isset(this_cpu, p->cpus_allowed))
if (!cpu_isset(this_cpu, p->cpus_allowed)) {
schedstat_inc(p, se.nr_failed_migrations_affine);
return 0;
}
*all_pinned = 0;

if (task_running(rq, p))
if (task_running(rq, p)) {
schedstat_inc(p, se.nr_failed_migrations_running);
return 0;
}

/*
* Aggressive migration if:
Expand All @@ -2163,14 +2191,18 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,

if (sd->nr_balance_failed > sd->cache_nice_tries) {
#ifdef CONFIG_SCHEDSTATS
if (task_hot(p, rq->clock, sd))
if (task_hot(p, rq->clock, sd)) {
schedstat_inc(sd, lb_hot_gained[idle]);
schedstat_inc(p, se.nr_forced_migrations);
}
#endif
return 1;
}

if (task_hot(p, rq->clock, sd))
if (task_hot(p, rq->clock, sd)) {
schedstat_inc(p, se.nr_failed_migrations_hot);
return 0;
}
return 1;
}

Expand Down
87 changes: 77 additions & 10 deletions kernel/sched_debug.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -260,6 +260,7 @@ __initcall(init_sched_debug_procfs);

void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
{
unsigned long nr_switches;
unsigned long flags;
int num_threads = 1;

Expand All @@ -273,15 +274,21 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid, num_threads);
SEQ_printf(m,
"---------------------------------------------------------\n");
#define __P(F) \
SEQ_printf(m, "%-35s:%21Ld\n", #F, (long long)F)
#define P(F) \
SEQ_printf(m, "%-35s:%21Ld\n", #F, (long long)p->F)
#define __PN(F) \
SEQ_printf(m, "%-35s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)F))
#define PN(F) \
SEQ_printf(m, "%-35s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)p->F))

PN(se.exec_start);
PN(se.vruntime);
PN(se.sum_exec_runtime);

nr_switches = p->nvcsw + p->nivcsw;

#ifdef CONFIG_SCHEDSTATS
PN(se.wait_start);
PN(se.sleep_start);
Expand All @@ -292,14 +299,55 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
PN(se.slice_max);
PN(se.wait_max);
P(sched_info.bkl_count);
P(se.nr_migrations);
P(se.nr_migrations_cold);
P(se.nr_failed_migrations_affine);
P(se.nr_failed_migrations_running);
P(se.nr_failed_migrations_hot);
P(se.nr_forced_migrations);
P(se.nr_forced2_migrations);
P(se.nr_wakeups);
P(se.nr_wakeups_sync);
P(se.nr_wakeups_migrate);
P(se.nr_wakeups_local);
P(se.nr_wakeups_remote);
P(se.nr_wakeups_affine);
P(se.nr_wakeups_affine_attempts);
P(se.nr_wakeups_passive);
P(se.nr_wakeups_idle);

{
u64 avg_atom, avg_per_cpu;

avg_atom = p->se.sum_exec_runtime;
if (nr_switches)
do_div(avg_atom, nr_switches);
else
avg_atom = -1LL;

avg_per_cpu = p->se.sum_exec_runtime;
if (p->se.nr_migrations)
avg_per_cpu = div64_64(avg_per_cpu, p->se.nr_migrations);
else
avg_per_cpu = -1LL;

__PN(avg_atom);
__PN(avg_per_cpu);
}
#endif
__P(nr_switches);
SEQ_printf(m, "%-35s:%21Ld\n",
"nr_switches", (long long)(p->nvcsw + p->nivcsw));
"nr_voluntary_switches", (long long)p->nvcsw);
SEQ_printf(m, "%-35s:%21Ld\n",
"nr_involuntary_switches", (long long)p->nivcsw);

P(se.load.weight);
P(policy);
P(prio);
#undef P
#undef PN
#undef __PN
#undef P
#undef __P

{
u64 t0, t1;
Expand All @@ -314,13 +362,32 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
void proc_sched_set_task(struct task_struct *p)
{
#ifdef CONFIG_SCHEDSTATS
p->se.sleep_max = 0;
p->se.block_max = 0;
p->se.exec_max = 0;
p->se.slice_max = 0;
p->se.wait_max = 0;
p->sched_info.bkl_count = 0;
p->se.wait_max = 0;
p->se.sleep_max = 0;
p->se.sum_sleep_runtime = 0;
p->se.block_max = 0;
p->se.exec_max = 0;
p->se.slice_max = 0;
p->se.nr_migrations = 0;
p->se.nr_migrations_cold = 0;
p->se.nr_failed_migrations_affine = 0;
p->se.nr_failed_migrations_running = 0;
p->se.nr_failed_migrations_hot = 0;
p->se.nr_forced_migrations = 0;
p->se.nr_forced2_migrations = 0;
p->se.nr_wakeups = 0;
p->se.nr_wakeups_sync = 0;
p->se.nr_wakeups_migrate = 0;
p->se.nr_wakeups_local = 0;
p->se.nr_wakeups_remote = 0;
p->se.nr_wakeups_affine = 0;
p->se.nr_wakeups_affine_attempts = 0;
p->se.nr_wakeups_passive = 0;
p->se.nr_wakeups_idle = 0;
p->sched_info.bkl_count = 0;
#endif
p->se.sum_exec_runtime = 0;
p->se.prev_sum_exec_runtime = 0;
p->se.sum_exec_runtime = 0;
p->se.prev_sum_exec_runtime = 0;
p->nvcsw = 0;
p->nivcsw = 0;
}

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