Re: [TEST] txtimestamp.sh pains after netdev foundation migration
From: Jakub Kicinski <kuba@kernel.org>
Date: 2026-01-08 16:06:47
Subsystem:
kernel selftest framework, networking [general], socket timestamping, the rest · Maintainers:
Shuah Khan, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Willem de Bruijn, Linus Torvalds
On Wed, 7 Jan 2026 19:25:11 -0800 Jakub Kicinski wrote:
On Wed, 07 Jan 2026 19:19:53 -0500 Willem de Bruijn wrote:quoted
17 out of 20 happen in the first SND-USR calculation. One representative example: # 7.11 [+0.00] test SND # 7.11 [+0.00] USR: 1767443466 s 155019 us (seq=0, len=0) # 7.19 [+0.08] ERROR: 18600 us expected between 10000 and 18000 # 7.19 [+0.00] SND: 1767443466 s 173619 us (seq=0, len=10) (USR +18599 us) # 7.20 [+0.00] USR: 1767443466 s 243683 us (seq=0, len=0) # 7.27 [+0.07] SND: 1767443466 s 253690 us (seq=1, len=10) (USR +10006 us) # 7.27 [+0.00] USR: 1767443466 s 323746 us (seq=0, len=0) # 7.35 [+0.08] SND: 1767443466 s 333752 us (seq=2, len=10) (USR +10006 us) # 7.35 [+0.00] USR: 1767443466 s 403811 us (seq=0, len=0) # 7.43 [+0.08] SND: 1767443466 s 413817 us (seq=3, len=10) (USR +10006 us) # 7.43 [+0.00] USR-SND: count=4, avg=12154 us, min=10006 us, max=18599 usHm, that's the first kernel timestamp vs the timestamp in user space? I wonder if we could catch this by re-taking the user stamp after sendmsg() returns, if >1msec elapsed something is probably wrong (we got scheduled out before having a chance to complete the send?)
How about:
diff --git a/tools/testing/selftests/net/txtimestamp.c b/tools/testing/selftests/net/txtimestamp.c
index 4b4bbc2ce5c9..abcec47ec2e6 100644
--- a/tools/testing/selftests/net/txtimestamp.c
+++ b/tools/testing/selftests/net/txtimestamp.c@@ -215,6 +215,24 @@ static void print_timestamp_usr(void) __print_timestamp(" USR", &ts_usr, 0, 0); } +static void check_timestamp_usr(void) +{ + long long unsigned ts_delta_usec; + struct timespec now; + + if (clock_gettime(CLOCK_REALTIME, &now)) + error(1, errno, "clock_gettime"); + + ts_delta_usec = timespec_to_ns64(&now) - timespec_to_ns64(&ts_usr); + ts_delta_usec /= 1000; + if (ts_delta_usec > cfg_delay_tolerance_usec / 2) { + cfg_delay_tolerance_usec = + ts_delta_usec + cfg_delay_tolerance_usec / 2; + fprintf(stderr, "WARN: sendmsg() took %llu us, increasing delay tolerance to %d us\n", + ts_delta_usec, cfg_delay_tolerance_usec); + } +} + static void print_timestamp(struct scm_timestamping *tss, int tstype, int tskey, int payload_len) {
@@ -678,6 +696,8 @@ static void do_test(int family, unsigned int report_opt) if (val != total_len) error(1, errno, "send"); + check_timestamp_usr(); + /* wait for all errors to be queued, else ACKs arrive OOO */ if (cfg_sleep_usec) usleep(cfg_sleep_usec);
--
2.52.0