perf_counter: Provide a way to enable counters on exec
This provides a way to mark a counter to be enabled on the next exec. This is useful for measuring the total activity of a program without including overhead from the process that launches it. This also changes the perf stat command to use this new facility. Signed-off-by: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <19017.43927.838745.689203@cargo.ozlabs.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -179,8 +179,9 @@ struct perf_counter_attr {
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comm : 1, /* include comm data */
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freq : 1, /* use freq, not period */
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inherit_stat : 1, /* per task counts */
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enable_on_exec : 1, /* next exec enables */
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__reserved_1 : 52;
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__reserved_1 : 51;
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__u32 wakeup_events; /* wakeup every n events */
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__u32 __reserved_2;
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@ -1428,6 +1428,53 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu)
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perf_counter_task_sched_in(curr, cpu);
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}
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/*
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* Enable all of a task's counters that have been marked enable-on-exec.
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* This expects task == current.
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*/
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static void perf_counter_enable_on_exec(struct task_struct *task)
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{
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struct perf_counter_context *ctx;
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struct perf_counter *counter;
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unsigned long flags;
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int enabled = 0;
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local_irq_save(flags);
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ctx = task->perf_counter_ctxp;
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if (!ctx || !ctx->nr_counters)
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goto out;
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__perf_counter_task_sched_out(ctx);
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spin_lock(&ctx->lock);
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list_for_each_entry(counter, &ctx->counter_list, list_entry) {
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if (!counter->attr.enable_on_exec)
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continue;
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counter->attr.enable_on_exec = 0;
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if (counter->state >= PERF_COUNTER_STATE_INACTIVE)
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continue;
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counter->state = PERF_COUNTER_STATE_INACTIVE;
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counter->tstamp_enabled =
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ctx->time - counter->total_time_enabled;
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enabled = 1;
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}
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/*
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* Unclone this context if we enabled any counter.
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*/
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if (enabled && ctx->parent_ctx) {
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put_ctx(ctx->parent_ctx);
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ctx->parent_ctx = NULL;
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}
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spin_unlock(&ctx->lock);
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perf_counter_task_sched_in(task, smp_processor_id());
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out:
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local_irq_restore(flags);
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}
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/*
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* Cross CPU call to read the hardware counter
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*/
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@ -2949,6 +2996,9 @@ void perf_counter_comm(struct task_struct *task)
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{
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struct perf_comm_event comm_event;
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if (task->perf_counter_ctxp)
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perf_counter_enable_on_exec(task);
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if (!atomic_read(&nr_comm_counters))
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return;
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@ -116,8 +116,9 @@ static void create_perf_stat_counter(int counter, int pid)
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fd[cpu][counter], strerror(errno));
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}
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} else {
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attr->inherit = inherit;
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attr->disabled = 1;
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attr->inherit = inherit;
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attr->disabled = 1;
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attr->enable_on_exec = 1;
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fd[0][counter] = sys_perf_counter_open(attr, pid, -1, -1, 0);
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if (fd[0][counter] < 0 && verbose)
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@ -262,7 +263,6 @@ static int run_perf_stat(int argc, const char **argv)
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* Enable counters and exec the command:
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*/
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t0 = rdclock();
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prctl(PR_TASK_PERF_COUNTERS_ENABLE);
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close(go_pipe[1]);
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wait(&status);
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