On Wed, Feb 1, 2023 at 10:26 PM Jon Doron <arilou@xxxxxxxxx> wrote:
>
> From: Jon Doron <jond@xxxxxx>
>
> Add option to set when the perf buffer should wake up, by default the
> perf buffer becomes signaled for every event that is being pushed to it.
>
> In case of a high throughput of events it will be more efficient to wake
> up only once you have X events ready to be read.
>
> So your application can wakeup once and drain the entire perf buffer.
>
> Signed-off-by: Jon Doron <jond@xxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 4 ++--
> tools/lib/bpf/libbpf.h | 3 ++-
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index eed5cec6f510..6b30ff13922b 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -11719,8 +11719,8 @@ struct perf_buffer *perf_buffer__new(int map_fd, size_t page_cnt,
> attr.config = PERF_COUNT_SW_BPF_OUTPUT;
> attr.type = PERF_TYPE_SOFTWARE;
> attr.sample_type = PERF_SAMPLE_RAW;
> - attr.sample_period = 1;
> - attr.wakeup_events = 1;
> + attr.sample_period = OPTS_GET(opts, wakeup_events, 1);
> + attr.wakeup_events = OPTS_GET(opts, wakeup_events, 1);
I suspect the case of
LIBBPF_OPTS(perf_buffer_opts, opts);
perf_buffer__new(...., &opts);
is not handled correctly and you end up with sample_period == wakeup_events == 0
Can you please add BPF selftests that's setting wakeup_events to zero
and separately to >1?
>
> p.attr = &attr;
> p.sample_cb = sample_cb;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 8777ff21ea1d..e83c0a915dc7 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -1246,8 +1246,9 @@ typedef void (*perf_buffer_lost_fn)(void *ctx, int cpu, __u64 cnt);
> /* common use perf buffer options */
> struct perf_buffer_opts {
> size_t sz;
> + __u32 wakeup_events;
> };
> -#define perf_buffer_opts__last_field sz
> +#define perf_buffer_opts__last_field wakeup_events
>
> /**
> * @brief **perf_buffer__new()** creates BPF perfbuf manager for a specified
> --
> 2.39.1
>
