On Tue, 05 Jun 2018 16:50:00 +0200, 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.
>
> Signed-off-by: Toke Høiland-Jørgensen <t...@toke.dk>
> ---
> tools/testing/selftests/bpf/trace_helpers.c | 47
> ++++++++++++++++++++++++++-
> tools/testing/selftests/bpf/trace_helpers.h | 4 ++
> 2 files changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/trace_helpers.c
> b/tools/testing/selftests/bpf/trace_helpers.c
> index 3868dcb63420..1e62d89f34cf 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 +168,41 @@ 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 = malloc(sizeof(*pfds) * num_fds);
> + if (!pfds)
> + return -1;
nit: this is correct, but better use LIBBPF_PERF_EVENT_ERROR? This
function is supposed to return enum bpf_perf_event_ret values I assume?
In case someone moves this code to libbpf later on...
> + memset(pfds, 0, sizeof(*pfds) * num_fds);
> + 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) {
nit: save yourself a lever of indentation by doing:
if (!pfds[i].revents)
continue;
and you won't have to go over 80 chars.
> + 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;
> +}
