Bug 998108 - Let's enable kvmclock in RHEL 6
Let's enable kvmclock in RHEL 6
Status: CLOSED ERRATA
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: libguestfs (Show other bugs)
6.5
Unspecified Unspecified
unspecified Severity unspecified
: rc
: ---
Assigned To: Richard W.M. Jones
Virtualization Bugs
:
Depends On:
Blocks: 998109
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Reported: 2013-08-17 05:36 EDT by Richard W.M. Jones
Modified: 2013-12-25 19:14 EST (History)
6 users (show)

See Also:
Fixed In Version: libguestfs-1.20.10-3.el6
Doc Type: Bug Fix
Doc Text:
Cause: Using libguestfs on heavily loaded machines. Consequence: You might see messages about "unstable clocks" appearing, especially in debugging output. Fix: Ensure that kvmclock is enabled. Result: Messages about "unstable clocks" should be reduced or eliminated by this change.
Story Points: ---
Clone Of: 998065
: 998109 (view as bug list)
Environment:
Last Closed: 2013-11-20 23:46:52 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
CRM:
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---


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Description Richard W.M. Jones 2013-08-17 05:36:34 EDT
+++ This bug was initially created as a clone of Bug #998065 +++

Upstream we switched over to using kvmclock (038ed0a08e & c53b459fdd).
We should do so in RHEL too since it would avoid most of
the trouble with clock instability.

https://github.com/libguestfs/libguestfs/commit/038ed0a08eaed33e62a27c9f91780a25de0bc08c
https://github.com/libguestfs/libguestfs/commit/c53b459fdd7fc340f48a76496b7e7e18256a2d64
Comment 1 bfan 2013-09-01 23:10:26 EDT
Hello Rich,
Could you tell me how can I tell it works?  I only find some message from boot debug logs.

"    
    -cpu host,+kvmclock \
    ...
    kvm-clock: Using msrs 4b564d01 and 4b564d00
    kvm-clock: cpu 0, msr 0:1c247c1, boot clock
    kvm-clock: cpu 0, msr 0:22167c1, primary cpu clock
    [    0.381003] Switching to clocksource kvm-clock
"
Is it enough?
Comment 2 Richard W.M. Jones 2013-09-02 10:33:46 EDT
(In reply to bfan from comment #1)
> Hello Rich,
> Could you tell me how can I tell it works?

https://rwmj.wordpress.com/2010/10/15/kvm-pvclock/#content

> I only find some message from
> boot debug logs.
> 
> "    
>     -cpu host,+kvmclock \
>     ...
>     kvm-clock: Using msrs 4b564d01 and 4b564d00
>     kvm-clock: cpu 0, msr 0:1c247c1, boot clock
>     kvm-clock: cpu 0, msr 0:22167c1, primary cpu clock
>     [    0.381003] Switching to clocksource kvm-clock
> "
> Is it enough?

This is sufficient to verify the bug fix IMHO.
Comment 4 bfan 2013-10-21 04:06:59 EDT
Verify this bug according to #comment 2
libguestfs-1.20.11-2.el6.x86_64

[root@dhcp-9-42 home]# guestfish -x -v -N fs > boot.log 2>&1
[root@dhcp-9-42 home]# cat boot.log | grep -Ei "kvmclock|kvm-clock"
    -cpu host,+kvmclock \
kvm-clock: Using msrs 4b564d01 and 4b564d00
kvm-clock: cpu 0, msr 0:1c247c1, boot clock
kvm-clock: cpu 0, msr 0:22167c1, primary cpu clock
[    0.153354] Switching to clocksource kvm-clock

So change the status to verified
Comment 6 errata-xmlrpc 2013-11-20 23:46:52 EST
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2013-1536.html

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