Re: [RFC PATCH 1/2] perf: Add the flag sample_disable not to output data on samples

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 10/12/2015 12:02 PM, Kaixu Xia wrote:

> In some scenarios we don't want to output trace data when sampling
> to reduce overhead. This patch adds the flag sample_disable to
> implement this function. By setting this flag and integrating with
> ebpf, we can control the data output process and get the samples we
> are most interested in.
>
> Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>

[...]
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index 29ace10..4ae82c9 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
[...]
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index b11756f..f6ef45c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6337,6 +6337,9 @@ static int __perf_event_overflow(struct perf_event *event,
>   		irq_work_queue(&event->pending);
>   	}
>
> +	if ((event->sample_disable) && atomic_read(event->sample_disable))

    Inner parens not needed at all.

[...]

MBR, Sergei