[PATCH v3 2/5] test: use fixed time length for write packet test

Stephen Hemminger
2026-02-28T17:56:21Z

This test would take excessively long if the TSC frequency
was very low. Instead of scaling test by frequency, just
use a fixed time length for the test.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
app/test/test_pcapng.c | 29 ++++++++++++++++++++---------
1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/app/test/test_pcapng.c b/app/test/test_pcapng.c
index f0faead728..af31e7d996 100644
--- a/app/test/test_pcapng.c
+++ b/app/test/test_pcapng.c
@@ -5,6 +5,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <time.h>

#ifdef RTE_EXEC_ENV_WINDOWS
#include <winsock2.h>
@@ -80,8 +81,16 @@ mkstemps(char *tmpl, int suffixlen)

#define PCAPNG_TEST_DEBUG 0

+/*
+ * Want to write enough packets to exercise timestamp logic.
+ * On fast CPU's TSC wraps around 32 bits in 4 seconds.
+ */
#define TOTAL_PACKETS 10000
-#define MAX_BURST 64
+#define MAX_BURST 32
+#define NUM_BURSTS (TOTAL_PACKETS / MAX_BURST)
+#define TEST_TIME_SEC 4
+#define GAP_US ((TEST_TIME_SEC * US_PER_S) / NUM_BURSTS)
+
#define DUMMY_MBUF_NUM 2

static struct rte_mempool *mp;
@@ -242,6 +251,7 @@ fill_pcapng_file(rte_pcapng_t *pcapng)
struct rte_mbuf *orig;
unsigned int burst_size;
unsigned int count;
+ struct timespec start_time;
ssize_t len;
/*
* These are some silly comments to test various lengths and alignments sprinkle
@@ -262,21 +272,22 @@ fill_pcapng_file(rte_pcapng_t *pcapng)
"generations of example code. The magic number 32 is not documented because "
"nobody remembers why. Trust the process."),
};
- /* How many microseconds does it take TSC to wrap around 32 bits */
- const unsigned wrap_us
- = (US_PER_S * (uint64_t)UINT32_MAX) / rte_get_tsc_hz();
-
- /* Want overall test to take to wraparound at least twice. */
- const unsigned int avg_gap = (2 * wrap_us)
- / (TOTAL_PACKETS / (MAX_BURST / 2));

mbuf1_prepare(&mbfs);
orig = &mbfs.mb[0];

+ clock_gettime(CLOCK_MONOTONIC, &start_time);
+
for (count = 0; count < TOTAL_PACKETS; count += burst_size) {
struct rte_mbuf *clones[MAX_BURST];
+ struct timespec now;
unsigned int i;

+ /* break off writing if test is taking too long */
+ clock_gettime(CLOCK_MONOTONIC, &now);
+ if (now.tv_sec >= start_time.tv_sec + TEST_TIME_SEC)
+ break;
+
/* put 1 .. MAX_BURST packets in one write call */
burst_size = rte_rand_max(MAX_BURST) + 1;
for (i = 0; i < burst_size; i++) {
@@ -309,7 +320,7 @@ fill_pcapng_file(rte_pcapng_t *pcapng)
return -1;
}

- rte_delay_us_block(rte_rand_max(2 * avg_gap));
+ rte_delay_us_block(rte_rand_max(2 * GAP_US));
}

return count;
--
2.51.0