linux-kernel - Re: [PATCH bpf-next 2/4] selftests/bpf: integrate test_tc_edt into test

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Message-Id: <09feef91b51f675195b5b1b9a854d844c9999c0cebb429d785fe60f6c787dc8b@mail.kernel.org>
Date: Fri, 31 Oct 2025 16:20:49 +0000 (UTC)
From: bot+bpf-ci@...nel.org
To: alexis.lothore@...tlin.com,ast@...nel.org,daniel@...earbox.net,andrii@...nel.org,martin.lau@...ux.dev,eddyz87@...il.com,song@...nel.org,yonghong.song@...ux.dev,john.fastabend@...il.com,kpsingh@...nel.org,sdf@...ichev.me,haoluo@...gle.com,jolsa@...nel.org,shuah@...nel.org
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Subject: Re: [PATCH bpf-next 2/4] selftests/bpf: integrate test_tc_edt into test_progs


```
commit fb0c5cfad37eaad30f584caaf53fe9824026bc92
Author: Alexis Lothoré (eBPF Foundation) <alexis.lothore@...tlin.com>

selftests/bpf: integrate test_tc_edt into test_progs

This patch converts test_tc_edt.sh to the test_progs framework,
creating a new test that measures BPF-based traffic shaping to verify
that the resulting rate matches 5Mbps within a 2% error margin.

> diff --git a/tools/testing/selftests/bpf/prog_tests/test_tc_edt.c b/tools/testing/selftests/bpf/prog_tests/test_tc_edt.c
> new file mode 100644
> index 000000000..a77e48fdf
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/test_tc_edt.c

[ ... ]

> +#define TARGET_RATE_MBPS	5.0
> +#define RATE_ERROR_PERCENT	2.0

[ ... ]

> +static void run_test(void)
> +{
> +	__u64 rx_bytes_start, rx_bytes_end;
> +	double rate_mbps, rate_error;
> +	pthread_t server_thread = 0;
> +	struct connection *conn;
> +	__u64 ts_start, ts_end;
> +	int ret;
> +
> +
> +	conn = setup_connection();
> +	if (!ASSERT_OK_PTR(conn, "setup client and server connection"))
> +		return;
> +
> +	ret = pthread_create(&server_thread, NULL, run_server,
> +			     (void *)(&conn->server_conn_fd));
> +	if (!ASSERT_OK(ret, "start server rx thread"))
> +		goto end_cleanup_conn;
> +	if (!ASSERT_OK(read_rx_bytes(&rx_bytes_start), "read rx_bytes"))
> +		goto end_kill_thread;
> +	ts_start = get_time_ns();
> +	while (true) {
> +		send(conn->client_conn_fd, (void *)tx_buffer, BUFFER_LEN, 0);
> +		ts_end = get_time_ns();
> +		if ((ts_end - ts_start)/100000 >= TIMEOUT_MS) {
                                         ^^^^^^

Does this time conversion use the correct divisor? The timeout check
appears to divide nanoseconds by 100000, but TIMEOUT_MS is 2000
milliseconds. Converting nanoseconds to milliseconds requires dividing
by 1000000, not 100000. With the current calculation, the timeout would
trigger after 200 milliseconds rather than 2000 milliseconds.

> +			tx_timeout = true;
> +			ret = read_rx_bytes(&rx_bytes_end);
> +			if (!ASSERT_OK(ret, "read_rx_bytes"))
> +				goto end_cleanup_conn;
> +			break;
> +		}
> +	}
> +
> +	rate_mbps = (rx_bytes_end - rx_bytes_start) /
> +		    ((ts_end - ts_start) / 1000.0);
                                       ^^^^^^

Can this rate calculation produce the correct units? The numerator is in
bytes, and the denominator (nanoseconds / 1000.0) is in microseconds,
giving bytes per microsecond which equals megabytes per second (MB/s).
However, the commit message states the test verifies "5Mbps" (megabits
per second), and TARGET_RATE_MBPS suggests the same. Converting MB/s to
Mbps requires multiplying by 8 (bits per byte), which appears to be
missing. Is the test measuring in the wrong units, or is there a naming
inconsistency?

> +	rate_error =
> +		fabs((rate_mbps - TARGET_RATE_MBPS) * 100.0 / TARGET_RATE_MBPS);
> +	fprintf(stderr, "Rate:\t%f\nError:\t%f\n", rate_mbps, rate_error);
> +
> +	ASSERT_LE(rate_error, RATE_ERROR_PERCENT,
> +		  "rate error is lower than threshold");
> +
> +end_kill_thread:
> +	tx_timeout = true;
> +end_cleanup_conn:
> +	cleanup_connection(conn);
> +}


```

---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

In-Reply-To-Subject: `selftests/bpf: integrate test_tc_edt into test_progs`
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/18978170972