timing ~ interrupts

kvm-clock (para-virtualized clock)

dmesg | grep kvm-clock

[    0.000000] kvm-clock: cpu 0, msr 0:141d0c1, boot clock
[    0.000000] kvm-clock: cpu 0, msr 0:1c080c1, primary cpu clock
[    0.132064] Switching to clocksource kvm-clock

cat /sys/devices/system/clocksource/clocksource0/current_clocksource

constant_TSC (Time Stamp Counter)   <-- kvm-clock 依賴它

grep constant_tsc /proc/cpuinfo

不受 cpufreq 及 Deep C sleep states 影響

Red Hat Enterprise Linux 6 does not have a fixed-frequency clock interrupt; it operates in tickless mode and

uses the timer dynamically as required. The divider parameter is therefore not useful for Red Hat Enterprise Linux 6

Windows uses the both the RTC and the TSC.

/usepmtimer          RTC

Guest Kernel

HIGH_RES_TIMER (High Resolution Timer Support )

HPET (High Precision Event Timer )

COMPACTION (Allows the compaction of memory for the allocation of huge pages )

MIGRATION

(migration of the physical location of pages of processes while the virtual addresses are not changed.)

KSM (Kernel Samepage Merging)

TRANSPARENT_HUGEPAGE(Transparent Hugepages)

VIRTIO_CONSOLE(Character devices at /dev/vportNpn)

data transfer between the guest and host.

HW_RANDOM_VIRTIO

virtual Random Number Generator hardware.

KVM_CLOCK