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perfcounters: add task migrations counter

Browse Source 
Impact: add new feature, new sw counter

Add a counter that counts the number of cross-CPU migrations a
task is suffering.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-12-14 12:34:15 +01:00
parent 5d6a27d8a0
commit 6c594c21fc
4 changed files with 61 additions and 6 deletions
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8
include/linux/perf_counter.h
View File

@ -42,6 +42,8 @@ enum hw_event_types {
PERF_COUNT_BRANCH_INSTRUCTIONS = 4,
PERF_COUNT_BRANCH_MISSES = 5,
PERF_HW_EVENTS_MAX = 6,
/*
* Special "software" counters provided by the kernel, even if
* the hardware does not support performance counters. These
@ -50,11 +52,11 @@ enum hw_event_types {
*/
PERF_COUNT_CPU_CLOCK = -1,
PERF_COUNT_TASK_CLOCK = -2,
/*
* Future software events:
*/
PERF_COUNT_PAGE_FAULTS = -3,
PERF_COUNT_CONTEXT_SWITCHES = -4,
PERF_COUNT_CPU_MIGRATIONS = -5,
PERF_SW_EVENTS_MIN = -6,
};
/*

3
include/linux/sched.h
View File

@ -1014,6 +1014,8 @@ struct sched_entity {
u64 last_wakeup;
u64 avg_overlap;
u64 nr_migrations;
#ifdef CONFIG_SCHEDSTATS
u64 wait_start;
u64 wait_max;
@ -1029,7 +1031,6 @@ struct sched_entity {
u64 exec_max;
u64 slice_max;
u64 nr_migrations;
u64 nr_migrations_cold;
u64 nr_failed_migrations_affine;
u64 nr_failed_migrations_running;

49
kernel/perf_counter.c
View File

@ -936,6 +936,52 @@ static const struct hw_perf_counter_ops perf_ops_context_switches = {
.hw_perf_counter_read = context_switches_perf_counter_read,
};
static inline u64 get_cpu_migrations(void)
{
return current->se.nr_migrations;
}
static void cpu_migrations_perf_counter_update(struct perf_counter *counter)
{
u64 prev, now;
s64 delta;
prev = atomic64_read(&counter->hw.prev_count);
now = get_cpu_migrations();
atomic64_set(&counter->hw.prev_count, now);
delta = now - prev;
if (WARN_ON_ONCE(delta < 0))
delta = 0;
atomic64_add(delta, &counter->count);
}
static void cpu_migrations_perf_counter_read(struct perf_counter *counter)
{
cpu_migrations_perf_counter_update(counter);
}
static void cpu_migrations_perf_counter_enable(struct perf_counter *counter)
{
/*
* se.nr_migrations is a per-task value already,
* so we dont have to clear it on switch-in.
*/
}
static void cpu_migrations_perf_counter_disable(struct perf_counter *counter)
{
cpu_migrations_perf_counter_update(counter);
}
static const struct hw_perf_counter_ops perf_ops_cpu_migrations = {
.hw_perf_counter_enable = cpu_migrations_perf_counter_enable,
.hw_perf_counter_disable = cpu_migrations_perf_counter_disable,
.hw_perf_counter_read = cpu_migrations_perf_counter_read,
};
static const struct hw_perf_counter_ops *
sw_perf_counter_init(struct perf_counter *counter)
{
@ -951,6 +997,9 @@ sw_perf_counter_init(struct perf_counter *counter)
case PERF_COUNT_CONTEXT_SWITCHES:
hw_ops = &perf_ops_context_switches;
break;
case PERF_COUNT_CPU_MIGRATIONS:
hw_ops = &perf_ops_cpu_migrations;
break;
default:
break;
}

7
kernel/sched.c
View File

@ -1852,12 +1852,14 @@ 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;
#endif
if (old_cpu != new_cpu) {
schedstat_inc(p, se.nr_migrations);
p->se.nr_migrations++;
#ifdef CONFIG_SCHEDSTATS
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;
@ -2375,6 +2377,7 @@ static void __sched_fork(struct task_struct *p)
p->se.exec_start = 0;
p->se.sum_exec_runtime = 0;
p->se.prev_sum_exec_runtime = 0;
p->se.nr_migrations = 0;
p->se.last_wakeup = 0;
p->se.avg_overlap = 0;