Hi, since I'm running a Debian Squeeze domU in a Citrix Xen dom0 with kernel 2.6.32-4-amd64 and having serious latency issues and audio hick-ups in longer calls, I've to look closer at timing issues. I didn't see any error messages or warnings, but maybe I don't have the right debug options set. # cat /sys/devices/system/clocksource/clocksource0/available_clocksource xen # cat /sys/devices/system/clocksource/clocksource0/current_clocksource xen The box is running chrony to provide accurate date&time. Below you'll find the output of timer_test, but I need some help interpreting this. In comparison to a bare metal box, the last column shows more "jitter" in the virtual box, but how bad are my values? According to a little program I found here: http://www.advenage.com/topics/linux-timer-interrupt-frequency.php : kernel timer interrupt frequency is approx. 4016 Hz or higher But how do I check the kernel timer resolution? All of this leaves me with the following questions: 1) Can I tweak the system to get better results? 2) Would it be better when using CentOS? Would I still have this problem, or would it be completely gone? 3) Is my latency problem (up to 30seconds of latency(!!!)) timer related, or do I have an other serious problem? There aren't any networking issues! Gigabit connections, private interconnect to the upstream provider and no packet loss at all. freeswitch@internal> timer_test Avg: 19.947ms Total Time: 999.762ms 2011-03-08 21:45:42.287865 [CONSOLE] mod_commands.c:461 Timer Test: samplecount after init: 1 freeswitch@internal> 2011-03-08 21:45:42.293298 [CONSOLE] mod_commands.c:466 Timer Test: samplecount after first step: 2 2011-03-08 21:45:42.312859 [CONSOLE] mod_commands.c:475 Timer Test: 1 sleep 20 19520 2011-03-08 21:45:42.333572 [CONSOLE] mod_commands.c:475 Timer Test: 2 sleep 20 20644 2011-03-08 21:45:42.353187 [CONSOLE] mod_commands.c:475 Timer Test: 3 sleep 20 19573 2011-03-08 21:45:42.373144 [CONSOLE] mod_commands.c:475 Timer Test: 4 sleep 20 19994 2011-03-08 21:45:42.393090 [CONSOLE] mod_commands.c:475 Timer Test: 5 sleep 20 19900 2011-03-08 21:45:42.412943 [CONSOLE] mod_commands.c:475 Timer Test: 6 sleep 20 19782 2011-03-08 21:45:42.432720 [CONSOLE] mod_commands.c:475 Timer Test: 7 sleep 20 19731 2011-03-08 21:45:42.452532 [CONSOLE] mod_commands.c:475 Timer Test: 8 sleep 20 19835 2011-03-08 21:45:42.473430 [CONSOLE] mod_commands.c:475 Timer Test: 9 sleep 20 20857 2011-03-08 21:45:42.493169 [CONSOLE] mod_commands.c:475 Timer Test: 10 sleep 20 19706 2011-03-08 21:45:42.512776 [CONSOLE] mod_commands.c:475 Timer Test: 11 sleep 20 19563 2011-03-08 21:45:42.533521 [CONSOLE] mod_commands.c:475 Timer Test: 12 sleep 20 20700 2011-03-08 21:45:42.553103 [CONSOLE] mod_commands.c:475 Timer Test: 13 sleep 20 19531 2011-03-08 21:45:42.572708 [CONSOLE] mod_commands.c:475 Timer Test: 14 sleep 20 19536 2011-03-08 21:45:42.593020 [CONSOLE] mod_commands.c:475 Timer Test: 15 sleep 20 20352 2011-03-08 21:45:42.612628 [CONSOLE] mod_commands.c:475 Timer Test: 16 sleep 20 19525 2011-03-08 21:45:42.633322 [CONSOLE] mod_commands.c:475 Timer Test: 17 sleep 20 20686 2011-03-08 21:45:42.652949 [CONSOLE] mod_commands.c:475 Timer Test: 18 sleep 20 19701 2011-03-08 21:45:42.672995 [CONSOLE] mod_commands.c:475 Timer Test: 19 sleep 20 19891 2011-03-08 21:45:42.693032 [CONSOLE] mod_commands.c:475 Timer Test: 20 sleep 20 19990 2011-03-08 21:45:42.713020 [CONSOLE] mod_commands.c:475 Timer Test: 21 sleep 20 19870 2011-03-08 21:45:42.732986 [CONSOLE] mod_commands.c:475 Timer Test: 22 sleep 20 19896 2011-03-08 21:45:42.752899 [CONSOLE] mod_commands.c:475 Timer Test: 23 sleep 20 19839 2011-03-08 21:45:42.772596 [CONSOLE] mod_commands.c:475 Timer Test: 24 sleep 20 19631 2011-03-08 21:45:42.793190 [CONSOLE] mod_commands.c:475 Timer Test: 25 sleep 20 20596 2011-03-08 21:45:42.812808 [CONSOLE] mod_commands.c:475 Timer Test: 26 sleep 20 19542 2011-03-08 21:45:42.833619 [CONSOLE] mod_commands.c:475 Timer Test: 27 sleep 20 20719 2011-03-08 21:45:42.853174 [CONSOLE] mod_commands.c:475 Timer Test: 28 sleep 20 19651 2011-03-08 21:45:42.872883 [CONSOLE] mod_commands.c:475 Timer Test: 29 sleep 20 19567 2011-03-08 21:45:42.893592 [CONSOLE] mod_commands.c:475 Timer Test: 30 sleep 20 20591 2011-03-08 21:45:42.913173 [CONSOLE] mod_commands.c:475 Timer Test: 31 sleep 20 19613 2011-03-08 21:45:42.932796 [CONSOLE] mod_commands.c:475 Timer Test: 32 sleep 20 19547 2011-03-08 21:45:42.953478 [CONSOLE] mod_commands.c:475 Timer Test: 33 sleep 20 20651 2011-03-08 21:45:42.973076 [CONSOLE] mod_commands.c:475 Timer Test: 34 sleep 20 19537 2011-03-08 21:45:42.992682 [CONSOLE] mod_commands.c:475 Timer Test: 35 sleep 20 19558 2011-03-08 21:45:43.013388 [CONSOLE] mod_commands.c:475 Timer Test: 36 sleep 20 20648 2011-03-08 21:45:43.033012 [CONSOLE] mod_commands.c:475 Timer Test: 37 sleep 20 19558 2011-03-08 21:45:43.052626 [CONSOLE] mod_commands.c:475 Timer Test: 38 sleep 20 19545 2011-03-08 21:45:43.073304 [CONSOLE] mod_commands.c:475 Timer Test: 39 sleep 20 20579 2011-03-08 21:45:43.092915 [CONSOLE] mod_commands.c:475 Timer Test: 40 sleep 20 19631 2011-03-08 21:45:43.112525 [CONSOLE] mod_commands.c:475 Timer Test: 41 sleep 20 19515 2011-03-08 21:45:43.133227 [CONSOLE] mod_commands.c:475 Timer Test: 42 sleep 20 20660 2011-03-08 21:45:43.152862 [CONSOLE] mod_commands.c:475 Timer Test: 43 sleep 20 19646 2011-03-08 21:45:43.173575 [CONSOLE] mod_commands.c:475 Timer Test: 44 sleep 20 20647 2011-03-08 21:45:43.193157 [CONSOLE] mod_commands.c:475 Timer Test: 45 sleep 20 19537 2011-03-08 21:45:43.212762 [CONSOLE] mod_commands.c:475 Timer Test: 46 sleep 20 19535 2011-03-08 21:45:43.233524 [CONSOLE] mod_commands.c:475 Timer Test: 47 sleep 20 20669 2011-03-08 21:45:43.252520 [CONSOLE] mod_commands.c:475 Timer Test: 48 sleep 20 19003 2011-03-08 21:45:43.273352 [CONSOLE] mod_commands.c:475 Timer Test: 49 sleep 20 20722 2011-03-08 21:45:43.293062 [CONSOLE] mod_commands.c:475 Timer Test: 50 sleep 20 19676 freeswitch@internal> timer_test 20 3 Avg: 19.792ms Total Time: 59.610ms 2011-03-08 21:48:34.467320 [CONSOLE] mod_commands.c:461 Timer Test: samplecount after init: 1 freeswitch@internal> 2011-03-08 21:48:34.473424 [CONSOLE] mod_commands.c:466 Timer Test: samplecount after first step: 2 2011-03-08 21:48:34.493299 [CONSOLE] mod_commands.c:475 Timer Test: 1 sleep 20 19738 2011-03-08 21:48:34.513203 [CONSOLE] mod_commands.c:475 Timer Test: 2 sleep 20 19833 2011-03-08 21:48:34.533075 [CONSOLE] mod_commands.c:475 Timer Test: 3 sleep 20 19805 On 29 Jan 2011, at 21:06, Chris Burns wrote:
Many Xen kernels are compiled with a lower resolution kernel timer. Most applications will not notice this, but a VoIP application doing async RTP probably will. It can make audio quality poor, especially if something other than FreeSWITCH is trying to get CPU time while you are handling media. That is the main reason that I found. I have had OK results with Xen with the proper configuration.