Bug 190961 - pvclock_gtod_notify invoked frequently leads to extra cpu load
Summary: pvclock_gtod_notify invoked frequently leads to extra cpu load
Alias: None
Product: Virtualization
Classification: Unclassified
Component: kvm (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: virtualization_kvm
Depends on:
Blocks: 178231
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Reported: 2016-12-23 08:39 UTC by Chen Yu
Modified: 2016-12-26 04:27 UTC (History)
0 users

See Also:
Kernel Version: 4.9
Regression: No
Bisected commit-id:


Description Chen Yu 2016-12-23 08:39:21 UTC
This thread is created for tracking purpose
Currently the notifier of pvclock_gtod_notify() get invoked
frequently due to the periodic update_wall_time(). This might
slow down the system a little bit as there might be redundant
execution code path and unnecessary lock contention
in update_pvclock_gtod(), which was found when I was doing
suspend/resume speed testings. As pvclock_gtod_notify()
should be invoked only when clocksource has changed, according to
Commit 16e8d74d2da9 ("KVM: x86: notifier for clocksource changes")
, either we can add a new notifier for clocksource switch,
or we can simply bypass the following code in pvclock_gtod_notify()
earlier if there is no clocksource switch.


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