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perfcounters: add context switch counter

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Impact: add new feature, new sw counter

Add a counter that counts the number of context-switches a task
is doing.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-12-14 12:28:33 +01:00
parent 8cb391e878
commit 5d6a27d8a0
2 changed files with 53 additions and 2 deletions
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4
include/linux/perf_counter.h
View File

@ -53,8 +53,8 @@ enum hw_event_types {
/*
* Future software events:
*/
/* PERF_COUNT_PAGE_FAULTS = -3,
PERF_COUNT_CONTEXT_SWITCHES = -4, */
PERF_COUNT_PAGE_FAULTS = -3,
PERF_COUNT_CONTEXT_SWITCHES = -4,
};
/*

51
kernel/perf_counter.c
View File

@ -888,6 +888,54 @@ static const struct hw_perf_counter_ops perf_ops_task_clock = {
.hw_perf_counter_read = task_clock_perf_counter_read,
};
static u64 get_context_switches(void)
{
struct task_struct *curr = current;
return curr->nvcsw + curr->nivcsw;
}
static void context_switches_perf_counter_update(struct perf_counter *counter)
{
u64 prev, now;
s64 delta;
prev = atomic64_read(&counter->hw.prev_count);
now = get_context_switches();
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 context_switches_perf_counter_read(struct perf_counter *counter)
{
context_switches_perf_counter_update(counter);
}
static void context_switches_perf_counter_enable(struct perf_counter *counter)
{
/*
* ->nvcsw + curr->nivcsw is a per-task value already,
* so we dont have to clear it on switch-in.
*/
}
static void context_switches_perf_counter_disable(struct perf_counter *counter)
{
context_switches_perf_counter_update(counter);
}
static const struct hw_perf_counter_ops perf_ops_context_switches = {
.hw_perf_counter_enable = context_switches_perf_counter_enable,
.hw_perf_counter_disable = context_switches_perf_counter_disable,
.hw_perf_counter_read = context_switches_perf_counter_read,
};
static const struct hw_perf_counter_ops *
sw_perf_counter_init(struct perf_counter *counter)
{
@ -900,6 +948,9 @@ sw_perf_counter_init(struct perf_counter *counter)
case PERF_COUNT_TASK_CLOCK:
hw_ops = &perf_ops_task_clock;
break;
case PERF_COUNT_CONTEXT_SWITCHES:
hw_ops = &perf_ops_context_switches;
break;
default:
break;
}