Bug 641915
| Summary: | backward time drift in RHEL4, 5, and 6 Xen HVM guests that use PM timer / bug in hypervisor routine pmt_update_time() [rhel-5.5.z] | ||
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| Product: | Red Hat Enterprise Linux 5 | Reporter: | RHEL Program Management <pm-rhel> |
| Component: | kernel-xen | Assignee: | Jiri Pirko <jpirko> |
| Status: | CLOSED ERRATA | QA Contact: | Red Hat Kernel QE team <kernel-qe> |
| Severity: | high | Docs Contact: | |
| Priority: | high | ||
| Version: | 5.5 | CC: | dhoward, drjones, jpirko, jzheng, llim, mrezanin, pbonzini, pm-eus, rkhan, uobergfe, xen-maint |
| Target Milestone: | rc | Keywords: | ZStream |
| Target Release: | --- | ||
| Hardware: | x86_64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: |
A Red Hat Enterprise Linux 4, 5, and 6 Xen HVM guest that uses PM timer for time keeping had the time drift backwards about 5 seconds per minute. This was caused by small inaccuracies in truncating in the pmt_update_time() function. With this update, time is kept accurately and no longer drifts backwards.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | 2010-11-09 18:09:29 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | 633028 | ||
| Bug Blocks: | |||
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Description
RHEL Program Management
2010-10-11 14:08:48 UTC
in kernel 2.6.18-194.21.1.el5 xen-hvm-correct-accuracy-of-pmtimer.patch I've tested the reproducer in the tracked bug. Issue reproduced on all the 3 guests - RHEL4, RHEL5, RHEL6 HVM with the specific kernels. I performed the test on kernel-xen-2.6.18-194.15.1.el5, selecting the PM timer in the guest, then running the constantly gettimeofday() code. At the beginning, I confirmed that the time difference between host and guest is no more than 2 seconds, simply using the date command. After running the program about 10 minutes, the difference has increased to about 50 to 60 seconds. Then I updated the kernel-xen package to kernel-xen-2.6.18-194.24.1.el5 from the errata link, rebooted the host and performed the test again. This time the time difference between host and guest has no noticeable change after running the program in the guest for more than 20 minutes. I also did this test on the 3 different guests simultaneously. Again the time drift issue does not occur on the new hypervisor, no matter how long the program runs. As a result I believe this bug could be put into VERIFIED. An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2010-0839.html
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New Contents:
A Red Hat Enterprise Linux 4, 5, and 6 Xen HVM guest that uses PM timer for time keeping had the time drift backwards about 5 seconds per minute. This was caused by small inaccuracies in truncating in the pmt_update_time() function. With this update, time is kept accurately and no longer drifts backwards.
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