[PATCH v3 5/8] perf: Split perf_event_read_value()

[Peter Zijlstra]

On Tue, Jul 14, 2015 at 08:01:52PM -0700, Sukadev Bhattiprolu wrote:
> Move the part of perf_event_read_value() that computes the event
> counts and event times into a new function, perf_event_compute().
> 
> This would allow us to call perf_event_compute() independently.
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> 
> Changelog[v3]
> 	Rather than move perf_event_read() into callers and then
> 	rename, just move the computations into a separate function
> 	(redesign to address comment from Peter Zijlstra).
> ---

Changelog[] bits go here, below the '---' where they get discarded.

>  kernel/events/core.c |   37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 44fb89d..b1e9a42 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3704,6 +3704,29 @@ static int perf_release(struct inode *inode, struct file *file)
>  	return 0;
>  }
>  
> +static u64 perf_event_compute(struct perf_event *event, u64 *enabled,
> +			      u64 *running)

This is a horrible name, 'compute' what?

> +{
> +	struct perf_event *child;
> +	u64 total;
> +
> +	total = perf_event_count(event);
> +
> +	*enabled += event->total_time_enabled +
> +			atomic64_read(&event->child_total_time_enabled);
> +	*running += event->total_time_running +
> +			atomic64_read(&event->child_total_time_running);
> +

	lockdep_assert_held(&event->child_mutex);

> +	list_for_each_entry(child, &event->child_list, child_list) {
> +		perf_event_read(child);
> +		total += perf_event_count(child);
> +		*enabled += child->total_time_enabled;
> +		*running += child->total_time_running;
> +	}
> +
> +	return total;
> +}
> +
>  /*
>   * Remove all orphanes events from the context.
>   */