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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>
This commit is contained in:
Paul Mackerras 2009-06-30 16:07:19 +10:00 committed by Ingo Molnar
parent 051ae7f734
commit 57e7986ed1
3 changed files with 55 additions and 4 deletions
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3
include/linux/perf_counter.h
View File

@ -179,8 +179,9 @@ struct perf_counter_attr {
comm : 1, /* include comm data */ comm : 1, /* include comm data */
freq : 1, /* use freq, not period */ freq : 1, /* use freq, not period */
inherit_stat : 1, /* per task counts */ inherit_stat : 1, /* per task counts */
enable_on_exec : 1, /* next exec enables */
__reserved_1 : 52; __reserved_1 : 51;
__u32 wakeup_events; /* wakeup every n events */ __u32 wakeup_events; /* wakeup every n events */
__u32 __reserved_2; __u32 __reserved_2;

50
kernel/perf_counter.c
View File

@ -1428,6 +1428,53 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu)
perf_counter_task_sched_in(curr, cpu); perf_counter_task_sched_in(curr, cpu);
} }
/*
* Enable all of a task's counters that have been marked enable-on-exec.
* This expects task == current.
*/
static void perf_counter_enable_on_exec(struct task_struct *task)
{
struct perf_counter_context *ctx;
struct perf_counter *counter;
unsigned long flags;
int enabled = 0;
local_irq_save(flags);
ctx = task->perf_counter_ctxp;
if (!ctx || !ctx->nr_counters)
goto out;
__perf_counter_task_sched_out(ctx);
spin_lock(&ctx->lock);
list_for_each_entry(counter, &ctx->counter_list, list_entry) {
if (!counter->attr.enable_on_exec)
continue;
counter->attr.enable_on_exec = 0;
if (counter->state >= PERF_COUNTER_STATE_INACTIVE)
continue;
counter->state = PERF_COUNTER_STATE_INACTIVE;
counter->tstamp_enabled =
ctx->time - counter->total_time_enabled;
enabled = 1;
}
/*
* Unclone this context if we enabled any counter.
*/
if (enabled && ctx->parent_ctx) {
put_ctx(ctx->parent_ctx);
ctx->parent_ctx = NULL;
}
spin_unlock(&ctx->lock);
perf_counter_task_sched_in(task, smp_processor_id());
out:
local_irq_restore(flags);
}
/* /*
* Cross CPU call to read the hardware counter * Cross CPU call to read the hardware counter
*/ */
@ -2949,6 +2996,9 @@ void perf_counter_comm(struct task_struct *task)
{ {
struct perf_comm_event comm_event; struct perf_comm_event comm_event;
if (task->perf_counter_ctxp)
perf_counter_enable_on_exec(task);
if (!atomic_read(&nr_comm_counters)) if (!atomic_read(&nr_comm_counters))
return; return;

6
tools/perf/builtin-stat.c
View File

@ -116,8 +116,9 @@ static void create_perf_stat_counter(int counter, int pid)
fd[cpu][counter], strerror(errno)); fd[cpu][counter], strerror(errno));
} }
} else { } else {
attr->inherit = inherit; attr->inherit = inherit;
attr->disabled = 1; attr->disabled = 1;
attr->enable_on_exec = 1;
fd[0][counter] = sys_perf_counter_open(attr, pid, -1, -1, 0); fd[0][counter] = sys_perf_counter_open(attr, pid, -1, -1, 0);
if (fd[0][counter] < 0 && verbose) if (fd[0][counter] < 0 && verbose)
@ -262,7 +263,6 @@ static int run_perf_stat(int argc, const char **argv)
* Enable counters and exec the command: * Enable counters and exec the command:
*/ */
t0 = rdclock(); t0 = rdclock();
prctl(PR_TASK_PERF_COUNTERS_ENABLE);
close(go_pipe[1]); close(go_pipe[1]);
wait(&status); wait(&status);