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perf_counter: Full task tracing

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In order to be able to distinguish between no samples due to
inactivity and no samples due to task ended, Arjan asked for
PERF_EVENT_EXIT events. This is useful to the boot delay
instrumentation (bootchart) app.

This patch changes the PERF_EVENT_FORK to be emitted on every
clone, and adds PERF_EVENT_EXIT to be emitted on task exit,
after the task's counters have been closed.

This task tracing is controlled through: attr.comm || attr.mmap
and through the new attr.task field.

Suggested-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ cleaned up perf_counter.h a bit ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-07-23 14:46:33 +02:00 committed by Ingo Molnar
parent e53c099470
commit 9f498cc5be
3 changed files with 84 additions and 46 deletions
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13
include/linux/perf_counter.h
View file

@ -181,8 +181,9 @@ struct perf_counter_attr {
freq : 1, /* use freq, not period */
inherit_stat : 1, /* per task counts */
enable_on_exec : 1, /* next exec enables */
task : 1, /* trace fork/exit */
__reserved_1 : 51;
__reserved_1 : 50;
__u32 wakeup_events; /* wakeup every n events */
__u32 __reserved_2;
@ -308,6 +309,15 @@ enum perf_event_type {
*/
PERF_EVENT_COMM = 3,
/*
* struct {
* struct perf_event_header header;
* u32 pid, ppid;
* u32 tid, ptid;
* };
*/
PERF_EVENT_EXIT = 4,
/*
* struct {
* struct perf_event_header header;
@ -323,6 +333,7 @@ enum perf_event_type {
* struct {
* struct perf_event_header header;
* u32 pid, ppid;
* u32 tid, ptid;
* };
*/
PERF_EVENT_FORK = 7,

4
kernel/fork.c
View file

@ -1269,6 +1269,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
write_unlock_irq(&tasklist_lock);
proc_fork_connector(p);
cgroup_post_fork(p);
perf_counter_fork(p);
return p;
bad_fork_free_pid:
@ -1410,9 +1411,6 @@ long do_fork(unsigned long clone_flags,
init_completion(&vfork);
}
if (!(clone_flags & CLONE_THREAD))
perf_counter_fork(p);
audit_finish_fork(p);
tracehook_report_clone(regs, clone_flags, nr, p);

113
kernel/perf_counter.c
View file

@ -42,6 +42,7 @@ static int perf_overcommit __read_mostly = 1;
static atomic_t nr_counters __read_mostly;
static atomic_t nr_mmap_counters __read_mostly;
static atomic_t nr_comm_counters __read_mostly;
static atomic_t nr_task_counters __read_mostly;
/*
* perf counter paranoia level:
@ -1654,6 +1655,8 @@ static void free_counter(struct perf_counter *counter)
atomic_dec(&nr_mmap_counters);
if (counter->attr.comm)
atomic_dec(&nr_comm_counters);
if (counter->attr.task)
atomic_dec(&nr_task_counters);
}
if (counter->destroy)
@ -2831,10 +2834,12 @@ perf_counter_read_event(struct perf_counter *counter,
}
/*
* fork tracking
* task tracking -- fork/exit
*
* enabled by: attr.comm | attr.mmap | attr.task
*/
struct perf_fork_event {
struct perf_task_event {
struct task_struct *task;
struct {
@ -2842,37 +2847,42 @@ struct perf_fork_event {
u32 pid;
u32 ppid;
u32 tid;
u32 ptid;
} event;
};
static void perf_counter_fork_output(struct perf_counter *counter,
struct perf_fork_event *fork_event)
static void perf_counter_task_output(struct perf_counter *counter,
struct perf_task_event *task_event)
{
struct perf_output_handle handle;
int size = fork_event->event.header.size;
struct task_struct *task = fork_event->task;
int size = task_event->event.header.size;
struct task_struct *task = task_event->task;
int ret = perf_output_begin(&handle, counter, size, 0, 0);
if (ret)
return;
fork_event->event.pid = perf_counter_pid(counter, task);
fork_event->event.ppid = perf_counter_pid(counter, task->real_parent);
task_event->event.pid = perf_counter_pid(counter, task);
task_event->event.ppid = perf_counter_pid(counter, task->real_parent);
perf_output_put(&handle, fork_event->event);
task_event->event.tid = perf_counter_tid(counter, task);
task_event->event.ptid = perf_counter_tid(counter, task->real_parent);
perf_output_put(&handle, task_event->event);
perf_output_end(&handle);
}
static int perf_counter_fork_match(struct perf_counter *counter)
static int perf_counter_task_match(struct perf_counter *counter)
{
if (counter->attr.comm || counter->attr.mmap)
if (counter->attr.comm || counter->attr.mmap || counter->attr.task)
return 1;
return 0;
}
static void perf_counter_fork_ctx(struct perf_counter_context *ctx,
struct perf_fork_event *fork_event)
static void perf_counter_task_ctx(struct perf_counter_context *ctx,
struct perf_task_event *task_event)
{
struct perf_counter *counter;
@ -2881,19 +2891,19 @@ static void perf_counter_fork_ctx(struct perf_counter_context *ctx,
rcu_read_lock();
list_for_each_entry_rcu(counter, &ctx->event_list, event_entry) {
if (perf_counter_fork_match(counter))
perf_counter_fork_output(counter, fork_event);
if (perf_counter_task_match(counter))
perf_counter_task_output(counter, task_event);
}
rcu_read_unlock();
}
static void perf_counter_fork_event(struct perf_fork_event *fork_event)
static void perf_counter_task_event(struct perf_task_event *task_event)
{
struct perf_cpu_context *cpuctx;
struct perf_counter_context *ctx;
cpuctx = &get_cpu_var(perf_cpu_context);
perf_counter_fork_ctx(&cpuctx->ctx, fork_event);
perf_counter_task_ctx(&cpuctx->ctx, task_event);
put_cpu_var(perf_cpu_context);
rcu_read_lock();
@ -2903,32 +2913,40 @@ static void perf_counter_fork_event(struct perf_fork_event *fork_event)
*/
ctx = rcu_dereference(current->perf_counter_ctxp);
if (ctx)
perf_counter_fork_ctx(ctx, fork_event);
perf_counter_task_ctx(ctx, task_event);
rcu_read_unlock();
}
static void perf_counter_task(struct task_struct *task, int new)
{
struct perf_task_event task_event;
if (!atomic_read(&nr_comm_counters) &&
!atomic_read(&nr_mmap_counters) &&
!atomic_read(&nr_task_counters))
return;
task_event = (struct perf_task_event){
.task = task,
.event = {
.header = {
.type = new ? PERF_EVENT_FORK : PERF_EVENT_EXIT,
.misc = 0,
.size = sizeof(task_event.event),
},
/* .pid */
/* .ppid */
/* .tid */
/* .ptid */
},
};
perf_counter_task_event(&task_event);
}
void perf_counter_fork(struct task_struct *task)
{
struct perf_fork_event fork_event;
if (!atomic_read(&nr_comm_counters) &&
!atomic_read(&nr_mmap_counters))
return;
fork_event = (struct perf_fork_event){
.task = task,
.event = {
.header = {
.type = PERF_EVENT_FORK,
.misc = 0,
.size = sizeof(fork_event.event),
},
/* .pid */
/* .ppid */
},
};
perf_counter_fork_event(&fork_event);
perf_counter_task(task, 1);
}
/*
@ -3887,6 +3905,8 @@ done:
atomic_inc(&nr_mmap_counters);
if (counter->attr.comm)
atomic_inc(&nr_comm_counters);
if (counter->attr.task)
atomic_inc(&nr_task_counters);
}
return counter;
@ -4248,8 +4268,10 @@ void perf_counter_exit_task(struct task_struct *child)
struct perf_counter_context *child_ctx;
unsigned long flags;
if (likely(!child->perf_counter_ctxp))
if (likely(!child->perf_counter_ctxp)) {
perf_counter_task(child, 0);
return;
}
local_irq_save(flags);
/*
@ -4267,15 +4289,22 @@ void perf_counter_exit_task(struct task_struct *child)
* incremented the context's refcount before we do put_ctx below.
*/
spin_lock(&child_ctx->lock);
child->perf_counter_ctxp = NULL;
/*
* If this context is a clone; unclone it so it can't get
* swapped to another process while we're removing all
* the counters from it.
*/
unclone_ctx(child_ctx);
spin_unlock(&child_ctx->lock);
local_irq_restore(flags);
spin_unlock_irqrestore(&child_ctx->lock, flags);
/*
* Report the task dead after unscheduling the counters so that we
* won't get any samples after PERF_EVENT_EXIT. We can however still
* get a few PERF_EVENT_READ events.
*/
perf_counter_task(child, 0);
child->perf_counter_ctxp = NULL;
/*
* We can recurse on the same lock type through: