> -----Ursprüngliche Nachricht----- > Von: Chen, Hongzhan [mailto:hongzhan.c...@intel.com] > Gesendet: Montag, 30. Mai 2022 02:56 > An: Prasanna Kannan <prasanna.kan...@ipg-automotive.com>; > xenomai@xenomai.org > Betreff: RE: Difference between Xenomai timer and Linux clock > > > > >-----Original Message----- > >From: Xenomai <xenomai-boun...@xenomai.org> On Behalf Of Prasanna > >Kannan via Xenomai > >Sent: Friday, May 27, 2022 9:39 PM > >To: xenomai@xenomai.org > >Subject: Difference between Xenomai timer and Linux clock > > > >Hello Everybody, > > > >I am comparing the Xenomai Timer(rt_timer_read()) and clock_gettime() > >with CLOCK_REALTIME and found that the two drift at roughly 100 us/s > >Here is the snippet from my code: > > > >init(): > >clock_gettime(CLOCK_REALTIME, &ts_start); rtime_start = > >rt_timer_read(); > > > >runtime(): > >clk_xenotime = (rt_timer_read() - rtime_start) * 1e-9; > >clock_gettime(CLOCK_REALTIME, &ts); clk_rttime = (ts.tv_sec - > >ts_start.tv_sec) + (ts.tv_nsec - > >ts_start.tv_nsec) * 1e-9; > >delta = clk_rttime - clk_xenotime > > > >The observation is that the delta is around 100us/s ... > >ClockGetTime:2.588435s, rt_timer_read:2.588167s, delta:0.000268s > >ClockGetTime:3.588533s, rt_timer_read:3.588161s, delta:0.000372s > >ClockGetTime:4.588671s, rt_timer_read:4.588196s, delta:0.000475s ... > > > >The Linux clock is not corrected via NTP/PTP, thus I am wondering why > >they are drifting in this way. > > > >Some Information about my setup: > >Xenomai/cobalt v3.1 > >Linux rtdonau 4.19.115-ipipe #54 SMP PREEMPT Wed Oct 13 12:16:56 CEST > >2021 > >x86_64 GNU/Linux > >Kernel parameters: intel_idle.max_cstate=0 vga=0x317 ip=dhcp > >root=/dev/nfs > >nfsroot=10.0.0.1:/opt/xyz/xeno_rt,tcp,nfsvers=3 BOOT_IMAGE=xeno10.2 > >I-pipe release #12 detected Cobalt core 3.1 detected > >Compiler: gcc version 7.5.0 (GCC) > >Build args: --prefix=/opt/xenomai-3.1 --enable-smp --enable-pshared > >--enable-dlopen-libs > > > >The hardware used is an Intel SBC based on Core i7-4700EQ CPU @ 2.40GHz > > One of what we found is that there is delayed work which would refine tsc > clock after Xenomai init and that cause Clock difference which may result in > such drift. The patchset "[Cobalt Xenoami3.1 PATCH 0/2] notify Xenomai > udpated clockfreq." > I sent in community at 5/27 try to fix what we found. Could you send your > complete linux dmsg to check if our issues is the same? > Yes, I can confirm this as I see similar messages in my linux dmesg: [ 0.000000] tsc: Detected 2394.479 MHz processor [ 1.714630] tsc: Refined TSC clocksource calibration: 2394.455 MHz
[rtdonau-~] !) cat /sys/module/xenomai/parameters/clockfreq 2394479000 Attached my complete dmesg. > Regards > > Hongzhan Chen > > > >Thank you in Advance. > > > >Best Regards > >Prasanna > > -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: dmesg_rtdonau.txt URL: <http://xenomai.org/pipermail/xenomai/attachments/20220530/e5d2e114/attachment.txt>
