Public bug reported:
[Impact]
The "force_latency=cstate.id:1|3" setting in the latency-performance profile
forces the CPU to remain in C-state 0 to achieve the desired latency.
This prevents the CPU from entering deeper idle states, causing the kernel to
switch the idle method to IDLE_POLL.
As a result, idle CPUs continuously busy-wait instead of entering power-saving
modes, leading to increased power consumption even when no tasks are being
processed.
[Fix]
Two upstream commits have already fixed this issue.
commit fc0dbea0db7af43f433b9d390c76a13b3cb2aaea
Author: Jan Zerdik <jzer...@redhat.com>
Date: Tue Feb 1 00:58:37 2022 +0100
Expanding cpu plugin force_latency option syntax
Adding "cstate.id_no_zero:X" and "cstate.name_no_zero:X" syntax to
force_latency option that skips given cstate if its latency is 0.
Resolves: rhbz#2034069
Resolves: rhbz#2002744
Signed-off-by: Jan Zerdik <jzer...@redhat.com>
commit 830d7b2d8dbf45c1f00656baf63576dbf95533c3
Author: Jaroslav Škarvada <jskar...@redhat.com>
Date: Tue Feb 1 18:35:17 2022 +0100
profiles: use cstate.id_no_zero instead of the cstate.id
Related: rhbz#2034069
Related: rhbz#2002744
Signed-off-by: Jaroslav Škarvada <jskar...@redhat.com>
[Test Plan]
1. Verify that the "force_latency" value in
/usr/lib/tuned/latency-performance/tuned.conf is set to
"cstate.id_no_zero:1|3".
2. Switch to the latency-performance tuning profile and ensure the latency is
set to the expected value.
tuned-adm profile latency-performance
tuned-adm active
hexdump /dev/cpu_dma_latency
3. Confirm that VMware VMs using the latency-performance profile do not
experience the same issue.
[Where problems could occur]
The patches adjust the latency logic in the latency-performance profile to
prevent the CPU from staying in C-state 0.
If any regressions occur, profiles using the "cstate.id_no_zero" setting may be
affected.
** Affects: tuned (Ubuntu)
Importance: Undecided
Status: New
** Affects: tuned (Ubuntu Focal)
Importance: Undecided
Status: New
** Affects: tuned (Ubuntu Jammy)
Importance: Undecided
Status: New
** Affects: tuned (Ubuntu Noble)
Importance: Undecided
Status: New
** Affects: tuned (Ubuntu Oracular)
Importance: Undecided
Status: New
** Affects: tuned (Ubuntu Plucky)
Importance: Undecided
Status: New
** Also affects: tuned (Ubuntu Noble)
Importance: Undecided
Status: New
** Also affects: tuned (Ubuntu Jammy)
Importance: Undecided
Status: New
** Also affects: tuned (Ubuntu Plucky)
Importance: Undecided
Status: New
** Also affects: tuned (Ubuntu Focal)
Importance: Undecided
Status: New
** Also affects: tuned (Ubuntu Oracular)
Importance: Undecided
Status: New
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Bugs, which is subscribed to Ubuntu.
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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