[RESEND,bpf-next,v6,1/2] trace_helpers.c: Add helpers to poll multiple perf FDs for events

Add two new helper functions to trace_helpers that supports polling
multiple perf file descriptors for events. These are used to the XDP
perf_event_output example, which needs to work with one perf fd per CPU.

Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
---
 tools/testing/selftests/bpf/trace_helpers.c |   48 ++++++++++++++++++++++++++-
 tools/testing/selftests/bpf/trace_helpers.h |    4 ++
 2 files changed, 50 insertions(+), 2 deletions(-)

On Mon, Jun 25, 2018 at 5:25 AM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> Add two new helper functions to trace_helpers that supports polling
> multiple perf file descriptors for events. These are used to the XDP
> perf_event_output example, which needs to work with one perf fd per CPU.
>
> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

Acked-by: Song Liu <songliubraving@fb.com>

> ---
>  tools/testing/selftests/bpf/trace_helpers.c |   48 ++++++++++++++++++++++++++-
>  tools/testing/selftests/bpf/trace_helpers.h |    4 ++
>  2 files changed, 50 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
> index 3868dcb63420..cabe2a3a3b30 100644
> --- a/tools/testing/selftests/bpf/trace_helpers.c
> +++ b/tools/testing/selftests/bpf/trace_helpers.c
> @@ -88,7 +88,7 @@ static int page_size;
>  static int page_cnt = 8;
>  static struct perf_event_mmap_page *header;
>
> -int perf_event_mmap(int fd)
> +int perf_event_mmap_header(int fd, struct perf_event_mmap_page **header)
>  {
>         void *base;
>         int mmap_size;
> @@ -102,10 +102,15 @@ int perf_event_mmap(int fd)
>                 return -1;
>         }
>
> -       header = base;
> +       *header = base;
>         return 0;
>  }
>
> +int perf_event_mmap(int fd)
> +{
> +       return perf_event_mmap_header(fd, &header);
> +}
> +
>  static int perf_event_poll(int fd)
>  {
>         struct pollfd pfd = { .fd = fd, .events = POLLIN };
> @@ -163,3 +168,42 @@ int perf_event_poller(int fd, perf_event_print_fn output_fn)
>
>         return ret;
>  }
> +
> +int perf_event_poller_multi(int *fds, struct perf_event_mmap_page **headers,
> +                           int num_fds, perf_event_print_fn output_fn)
> +{
> +       enum bpf_perf_event_ret ret;
> +       struct pollfd *pfds;
> +       void *buf = NULL;
> +       size_t len = 0;
> +       int i;
> +
> +       pfds = calloc(num_fds, sizeof(*pfds));
> +       if (!pfds)
> +               return LIBBPF_PERF_EVENT_ERROR;
> +
> +       for (i = 0; i < num_fds; i++) {
> +               pfds[i].fd = fds[i];
> +               pfds[i].events = POLLIN;
> +       }
> +
> +       for (;;) {
> +               poll(pfds, num_fds, 1000);
> +               for (i = 0; i < num_fds; i++) {
> +                       if (!pfds[i].revents)
> +                               continue;
> +
> +                       ret = bpf_perf_event_read_simple(headers[i],
> +                                                        page_cnt * page_size,
> +                                                        page_size, &buf, &len,
> +                                                        bpf_perf_event_print,
> +                                                        output_fn);
> +                       if (ret != LIBBPF_PERF_EVENT_CONT)
> +                               break;
> +               }
> +       }
> +       free(buf);
> +       free(pfds);
> +
> +       return ret;
> +}
> diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h
> index 3b4bcf7f5084..18924f23db1b 100644
> --- a/tools/testing/selftests/bpf/trace_helpers.h
> +++ b/tools/testing/selftests/bpf/trace_helpers.h
> @@ -3,6 +3,7 @@
>  #define __TRACE_HELPER_H
>
>  #include <libbpf.h>
> +#include <linux/perf_event.h>
>
>  struct ksym {
>         long addr;
> @@ -16,6 +17,9 @@ long ksym_get_addr(const char *name);
>  typedef enum bpf_perf_event_ret (*perf_event_print_fn)(void *data, int size);
>
>  int perf_event_mmap(int fd);
> +int perf_event_mmap_header(int fd, struct perf_event_mmap_page **header);
>  /* return LIBBPF_PERF_EVENT_DONE or LIBBPF_PERF_EVENT_ERROR */
>  int perf_event_poller(int fd, perf_event_print_fn output_fn);
> +int perf_event_poller_multi(int *fds, struct perf_event_mmap_page **headers,
> +                           int num_fds, perf_event_print_fn output_fn);
>  #endif
>

On 06/25/2018 02:25 PM, Toke Høiland-Jørgensen wrote:
> Add two new helper functions to trace_helpers that supports polling
> multiple perf file descriptors for events. These are used to the XDP
> perf_event_output example, which needs to work with one perf fd per CPU.
> 
> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

Both applied to bpf-next, thanks Toke!