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 <xiaka...@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

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