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SubjectRe: [PATCH bpf-next 1/5] perf/core: Add PERF_FORMAT_LOST read_format
On Tue, Sep 17, 2019 at 06:30:52AM -0700, Daniel Xu wrote:

SNIP

> + PERF_FORMAT_MAX = 1U << 5, /* non-ABI */
> };
>
> #define PERF_ATTR_SIZE_VER0 64 /* sizeof first published struct */
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 0463c1151bae..ee08d3ed6299 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1715,6 +1715,9 @@ static void __perf_event_read_size(struct perf_event *event, int nr_siblings)
> if (event->attr.read_format & PERF_FORMAT_ID)
> entry += sizeof(u64);
>
> + if (event->attr.read_format & PERF_FORMAT_LOST)
> + entry += sizeof(u64);
> +
> if (event->attr.read_format & PERF_FORMAT_GROUP) {
> nr += nr_siblings;
> size += sizeof(u64);
> @@ -4734,6 +4737,24 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
> }
> EXPORT_SYMBOL_GPL(perf_event_read_value);
>
> +static struct pmu perf_kprobe;
> +static u64 perf_event_lost(struct perf_event *event)
> +{
> + struct ring_buffer *rb;
> + u64 lost = 0;
> +
> + rcu_read_lock();
> + rb = rcu_dereference(event->rb);
> + if (likely(!!rb))
> + lost += local_read(&rb->lost);
> + rcu_read_unlock();
> +
> + if (event->attr.type == perf_kprobe.type)
> + lost += perf_kprobe_missed(event);

not sure what was the peterz's suggestion, but here you are mixing
ring buffer's lost count with kprobes missed count, seems wrong

maybe we could add PERF_FORMAT_KPROBE_MISSED

jirka

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