a) Is this bug only present in vmware guests? No other systems?
So far, only VMware virtual machines have been affected by this issue. No other
systems have been reported to encounter it at this time.
b) What is the impact of this change on non-vmware guests?
The impact depends on the value of
/sys/devices/system/cpu/cpu0/cpuidle/state1/latency. If the value is non-zero,
the behavior remains unchanged. However, if it is set to zero, a system-level
fix is also required to prevent the kernel from switching the idle method to
IDLE_POLL.
c) Does the change still achieve the desired outcome of low latency and high
performance, or is any of those two variables affected in a negative way?
d) Isn't it expected to have higher power consumption when one wants high
performance and low latency?
In my opinion, the overall logic remains the same, but this patch addresses an
exception where the latency of C-state 1 is zero. The intention may be to
reduce CPU stress in this specific scenario.
e) Will the proposed change be in effect right after the package is upgraded,
or is the user supposed to run a command?
Upgrading the package will cause systemd to restart the tuned service
automatically. The new configuration will be applied without requiring any
additional commands.
f) The diff is also showing changes to other profiles: sap-hana, and
virtual-host. Not just latency-performance. Is that expected?
The patch is identical to the one in the upstream commit. In my opinion, it
would be reasonable to align the profile settings with the upstream behavior.
** Changed in: tuned (Ubuntu Jammy)
Status: Incomplete => In Progress
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https://bugs.launchpad.net/bugs/2103840
Title:
VMware VMs experience 100% CPU usage when the latency-performance
tuned profile is enabled
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