Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling

From: Alexei Starovoitov <ast@plumgrid.com>
To: Kaixu Xia <xiakaixu@huawei.com>,
	davem@davemloft.net, acme@kernel.org, mingo@redhat.com,
	a.p.zijlstra@chello.nl, masami.hiramatsu.pt@hitachi.com,
	jolsa@kernel.org, daniel@iogearbox.net
Cc: wangnan0@huawei.com, linux-kernel@vger.kernel.org,
	pi3orama@163.com, hekuang@huawei.com, netdev@vger.kernel.org
Subject: Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling
Date: Tue, 20 Oct 2015 15:53:02 -0700	[thread overview]
Message-ID: <5626C5CE.8080809@plumgrid.com> (raw)
In-Reply-To: <1445325735-121694-2-git-send-email-xiakaixu@huawei.com>

On 10/20/15 12:22 AM, Kaixu Xia wrote:
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index b11756f..5219635 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 (unlikely(!atomic_read(&event->soft_enable)))
> +		return 0;
> +
>   	if (event->overflow_handler)
>   		event->overflow_handler(event, data, regs);
>   	else

Peter,
does this part look right or it should be moved right after
if (unlikely(!is_sampling_event(event)))
                 return 0;
or even to other function?

It feels to me that it should be moved, since we probably don't
want to active throttling, period adjust and event_limit for events
that are in soft_disabled state.