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perf_counter: rework context time

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Since perf_counter_context is switched along with tasks, we can
maintain the context time without using the task runtime clock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094518.353552838@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-04-06 11:45:10 +02:00 • committed by Ingo Molnar
commit 4af4998b8a
2 changed files with 37 additions and 51 deletions
Download patch file Download diff file Expand all files Collapse all files

10
include/linux/perf_counter.h
View file

@ -477,14 +477,10 @@ struct perf_counter_context {
struct task_struct *task;
/*
* time_now is the current time in nanoseconds since an arbitrary
* point in the past. For per-task counters, this is based on the
* task clock, and for per-cpu counters it is based on the cpu clock.
* time_lost is an offset from the task/cpu clock, used to make it
* appear that time only passes while the context is scheduled in.
* Context clock, runs when context enabled.
*/
u64 time_now;
u64 time_lost;
u64 time;
u64 timestamp;
#endif
};

68
kernel/perf_counter.c
View file

@ -117,7 +117,7 @@ counter_sched_out(struct perf_counter *counter,
return;
counter->state = PERF_COUNTER_STATE_INACTIVE;
counter->tstamp_stopped = ctx->time_now;
counter->tstamp_stopped = ctx->time;
counter->hw_ops->disable(counter);
counter->oncpu = -1;
@ -253,27 +253,20 @@ retry:
spin_unlock_irq(&ctx->lock);
}
/*
* Get the current time for this context.
* If this is a task context, we use the task's task clock,
* or for a per-cpu context, we use the cpu clock.
*/
static u64 get_context_time(struct perf_counter_context *ctx, int update)
static inline u64 perf_clock(void)
{
struct task_struct *curr = ctx->task;
if (!curr)
return cpu_clock(smp_processor_id());
return __task_delta_exec(curr, update) + curr->se.sum_exec_runtime;
}
/*
* Update the record of the current time in a context.
*/
static void update_context_time(struct perf_counter_context *ctx, int update)
static void update_context_time(struct perf_counter_context *ctx)
{
ctx->time_now = get_context_time(ctx, update) - ctx->time_lost;
u64 now = perf_clock();
ctx->time += now - ctx->timestamp;
ctx->timestamp = now;
}
/*
@ -284,16 +277,18 @@ static void update_counter_times(struct perf_counter *counter)
struct perf_counter_context *ctx = counter->ctx;
u64 run_end;
if (counter->state >= PERF_COUNTER_STATE_INACTIVE) {
counter->total_time_enabled = ctx->time_now -
counter->tstamp_enabled;
if (counter->state < PERF_COUNTER_STATE_INACTIVE)
return;
counter->total_time_enabled = ctx->time - counter->tstamp_enabled;
if (counter->state == PERF_COUNTER_STATE_INACTIVE)
run_end = counter->tstamp_stopped;
else
run_end = ctx->time_now;
run_end = ctx->time;
counter->total_time_running = run_end - counter->tstamp_running;
}
}
/*
* Update total_time_enabled and total_time_running for all counters in a group.
@ -332,7 +327,7 @@ static void __perf_counter_disable(void *info)
* If it is in error state, leave it in error state.
*/
if (counter->state >= PERF_COUNTER_STATE_INACTIVE) {
update_context_time(ctx, 1);
update_context_time(ctx);
update_counter_times(counter);
if (counter == counter->group_leader)
group_sched_out(counter, cpuctx, ctx);
@ -426,7 +421,7 @@ counter_sched_in(struct perf_counter *counter,
return -EAGAIN;
}
counter->tstamp_running += ctx->time_now - counter->tstamp_stopped;
counter->tstamp_running += ctx->time - counter->tstamp_stopped;
if (!is_software_counter(counter))
cpuctx->active_oncpu++;
@ -493,9 +488,9 @@ static void add_counter_to_ctx(struct perf_counter *counter,
list_add_counter(counter, ctx);
ctx->nr_counters++;
counter->prev_state = PERF_COUNTER_STATE_OFF;
counter->tstamp_enabled = ctx->time_now;
counter->tstamp_running = ctx->time_now;
counter->tstamp_stopped = ctx->time_now;
counter->tstamp_enabled = ctx->time;
counter->tstamp_running = ctx->time;
counter->tstamp_stopped = ctx->time;
}
/*
@ -522,7 +517,7 @@ static void __perf_install_in_context(void *info)
curr_rq_lock_irq_save(&flags);
spin_lock(&ctx->lock);
update_context_time(ctx, 1);
update_context_time(ctx);
/*
* Protect the list operation against NMI by disabling the
@ -648,13 +643,13 @@ static void __perf_counter_enable(void *info)
curr_rq_lock_irq_save(&flags);
spin_lock(&ctx->lock);
update_context_time(ctx, 1);
update_context_time(ctx);
counter->prev_state = counter->state;
if (counter->state >= PERF_COUNTER_STATE_INACTIVE)
goto unlock;
counter->state = PERF_COUNTER_STATE_INACTIVE;
counter->tstamp_enabled = ctx->time_now - counter->total_time_enabled;
counter->tstamp_enabled = ctx->time - counter->total_time_enabled;
/*
* If the counter is in a group and isn't the group leader,
@ -737,8 +732,8 @@ static void perf_counter_enable(struct perf_counter *counter)
*/
if (counter->state == PERF_COUNTER_STATE_OFF) {
counter->state = PERF_COUNTER_STATE_INACTIVE;
counter->tstamp_enabled = ctx->time_now -
counter->total_time_enabled;
counter->tstamp_enabled =
ctx->time - counter->total_time_enabled;
}
out:
spin_unlock_irq(&ctx->lock);
@ -778,7 +773,7 @@ void __perf_counter_sched_out(struct perf_counter_context *ctx,
ctx->is_active = 0;
if (likely(!ctx->nr_counters))
goto out;
update_context_time(ctx, 0);
update_context_time(ctx);
flags = hw_perf_save_disable();
if (ctx->nr_active) {
@ -883,12 +878,7 @@ __perf_counter_sched_in(struct perf_counter_context *ctx,
if (likely(!ctx->nr_counters))
goto out;
/*
* Add any time since the last sched_out to the lost time
* so it doesn't get included in the total_time_enabled and
* total_time_running measures for counters in the context.
*/
ctx->time_lost = get_context_time(ctx, 0) - ctx->time_now;
ctx->timestamp = perf_clock();
flags = hw_perf_save_disable();
@ -1043,8 +1033,8 @@ int perf_counter_task_enable(void)
if (counter->state > PERF_COUNTER_STATE_OFF)
continue;
counter->state = PERF_COUNTER_STATE_INACTIVE;
counter->tstamp_enabled = ctx->time_now -
counter->total_time_enabled;
counter->tstamp_enabled =
ctx->time - counter->total_time_enabled;
counter->hw_event.disabled = 0;
}
hw_perf_restore(perf_flags);
@ -1113,7 +1103,7 @@ static void __read(void *info)
curr_rq_lock_irq_save(&flags);
if (ctx->is_active)
update_context_time(ctx, 1);
update_context_time(ctx);
counter->hw_ops->read(counter);
update_counter_times(counter);
curr_rq_unlock_irq_restore(&flags);