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ntp: delay enabling permanent kernel RX timestamping on Linux

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Wait until a kernel RX timestamp is actually missing before opening the
dummy socket in order to avoid a small performance impact in case the
servers are so slow/distant that the kernel can constantly win the race.
This commit is contained in:
Miroslav Lichvar 2018-03-02 11:49:53 +01:00
parent 8e4c776900
commit 8b1f68b1b4
1 changed files with 9 additions and 3 deletions
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12
ntp_io_linux.c
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@ -397,9 +397,7 @@ NIO_Linux_Initialise(void)
monitored_socket = INVALID_SOCK_FD;
suspended_socket = INVALID_SOCK_FD;
/* Open a socket to keep the kernel RX timestamping permanently enabled */
dummy_rxts_socket = open_dummy_socket();
dummy_rxts_socket = INVALID_SOCK_FD;
}
/* ================================================== */
@ -763,6 +761,14 @@ NIO_Linux_ProcessMessage(NTP_Remote_Address *remote_addr, NTP_Local_Address *loc
}
}
/* If the kernel is slow with enabling RX timestamping, open a dummy
socket to keep the kernel RX timestamping permanently enabled */
if (!is_tx && local_ts->source == NTP_TS_DAEMON && ts_flags) {
DEBUG_LOG("Missing kernel RX timestamp");
if (dummy_rxts_socket == INVALID_SOCK_FD)
dummy_rxts_socket = open_dummy_socket();
}
/* Return the message if it's not received from the error queue */
if (!is_tx)
return 0;