Re: [PATCH v2 4/4] selftests: net: udpgso_bench_tx: Cater for pending datagrams zerocopy benchmarking

Paolo Abeni
2023-01-31T14:52:53Z

On Tue, 2023-01-31 at 13:04 +0000, Andrei Gherzan wrote:
> The test tool can check that the zerocopy number of completions value is
> valid taking into consideration the number of datagram send calls. This can
> catch the system into a state where the datagrams are still in the system
> (for example in a qdisk, waiting for the network interface to return a
> completion notification, etc).
>
> This change adds a retry logic of computing the number of completions up to
> a configurable (via CLI) timeout (default: 2 seconds).
>
> Signed-off-by: Andrei Gherzan <andrei.gherzan@canonical.com>
> ---
> tools/testing/selftests/net/udpgso_bench_tx.c | 38 +++++++++++++++----
> 1 file changed, 30 insertions(+), 8 deletions(-)
>
> diff --git a/tools/testing/selftests/net/udpgso_bench_tx.c b/tools/testing/selftests/net/udpgso_bench_tx.c
> index b47b5c32039f..5a29b5f24023 100644
> --- a/tools/testing/selftests/net/udpgso_bench_tx.c
> +++ b/tools/testing/selftests/net/udpgso_bench_tx.c
> @@ -62,6 +62,7 @@ static int cfg_payload_len = (1472 * 42);
> static int cfg_port = 8000;
> static int cfg_runtime_ms = -1;
> static bool cfg_poll;
> +static int cfg_poll_loop_timeout_ms = 2000;
> static bool cfg_segment;
> static bool cfg_sendmmsg;
> static bool cfg_tcp;
> @@ -235,16 +236,17 @@ static void flush_errqueue_recv(int fd)
> }
> }
>
> -static void flush_errqueue(int fd, const bool do_poll)
> +static void flush_errqueue(int fd, const bool do_poll,
> + unsigned long poll_timeout, const bool poll_err)
> {
> if (do_poll) {
> struct pollfd fds = {0};
> int ret;
>
> fds.fd = fd;
> - ret = poll(&fds, 1, 500);
> + ret = poll(&fds, 1, poll_timeout);
> if (ret == 0) {
> - if (cfg_verbose)
> + if ((cfg_verbose) && (poll_err))
> fprintf(stderr, "poll timeout\n");
> } else if (ret < 0) {
> error(1, errno, "poll");
> @@ -254,6 +256,22 @@ static void flush_errqueue(int fd, const bool do_poll)
> flush_errqueue_recv(fd);
> }
>
> +static void flush_errqueue_retry(int fd, const bool do_poll, unsigned long num_sends)
> +{
> + unsigned long tnow, tstop;
> + bool first_try = true;
> +
> + tnow = gettimeofday_ms();
> + tstop = tnow + cfg_poll_loop_timeout_ms;
> + do {
> + flush_errqueue(fd, do_poll, tstop - tnow, first_try);
> + first_try = false;
> + if (!do_poll)
> + usleep(1000); // a throttling delay if polling is enabled

Even if the kernel codying style is not very strictly enforced for
self-tests, please avoid c++ style comments.

More importantly, as Willem noded, this function is always called with
do_poll == true. You should drop such argument and the related branch
above.

> + tnow = gettimeofday_ms();
> + } while ((stat_zcopies != num_sends) && (tnow < tstop));
> +}
> +
> static int send_tcp(int fd, char *data)
> {
> int ret, done = 0, count = 0;
> @@ -413,8 +431,9 @@ static int send_udp_segment(int fd, char *data)
>
> static void usage(const char *filepath)
> {
> - error(1, 0, "Usage: %s [-46acmHPtTuvz] [-C cpu] [-D dst ip] [-l secs] [-M messagenr] [-p port] [-s sendsize] [-S gsosize]",
> - filepath);
> + error(1, 0,
> + "Usage: %s [-46acmHPtTuvz] [-C cpu] [-D dst ip] [-l secs] [-L secs] [-M messagenr] [-p port] [-s sendsize] [-S gsosize]",
> + filepath);

Please avoid introducing unnecessary white-space changes (no reason to
move the usage text on a new line)

Cheers,

Paolo