The problem exists in 4.19.rc7 I just tried.
So overall, I'm not sure now if this is a "different state" of the
system, or just a normal behavior of it.
Fresh after boot, the CPU is willing to use frequencies above 3 GHz. The
same when I launch my IDE (IntelliJ idea for the first time). Then when
I hit "rebuild project" to compile all the stuff, the frequency goes up
to 3+ GHz for a short while, and after just 2-4 seconds it drops back to
about 1.3-1.6 GHz and stays at this level for the whole build (several
minutes). The temperatures reported by i7z do not go above 54 C on any
of the cores, and VCore is kept around 0.69 - 0.71.
What does not look right to me are very high numbers reported in the Halt (C1)
column at the same time when C0 column reports numbers > 90. Typically C1
numbers are over 50, and some hit 90+.
This doesn't make much sense to me, because I thought C1 and C0 are distinct
(either/or, the core cannot be in both at the same time).
When the system is loaded by background compilation of my project, the
CPU is not willing to use higher frequencies even when I add more load
to it temporarily.
I compiled a really simple code doing an infinite loop:
int main() {
for (;;);
return 0;
}
Now running this program on an idle system makes the CPU frequency go to
about 2.8 GHz. C0 states are reported at less than 5, C1 states for all
cores are > 95 and temperatures are < 53.
Interestingly running this same program when the system is compiling in
background does not increase the frequencies above 1.6 GHz. If it is
loaded, it is unwilling to go faster. :D
So to summarize the CPU is capable to use higher frequencies for a very
short span of time, but then the performance quickly degrades under load
and stays there.
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https://bugs.launchpad.net/bugs/1797802
Title:
Erratic behavior of intel pstate CPU frequency control
Status in linux package in Ubuntu:
Incomplete
Bug description:
I noticed that sometimes my Ubuntu 18.10 system feels sluggish. The
other times everything works fine. I don't know what triggers this
weird state. Suspend / resume? Maybe.
At first I thought this was maybe just a "perception issue", but then
when the sluggishness happened again, I fired up i7z and it looks that
CPU frequency almost never got over ~1600 MHz, But my CPU is perfectly
capable of going up to 4000 MHz!
I tried to fix it by setting
echo 80 > /sys/devices/system/cpu/intel_pstate/min_perf_pct
echo 80 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
I hoped I would force the CPU into almost max performance state this
way. And indeed, once I ran these commands, i7z showed steady 3100+
MHz on all cores.
Then something weird happened - when I run some mild load on the CPU,
like just starting the IDE, during the startup the frequency **
dropped back to about 800-1600 MHz ** and returned to 3100 MHz after
the load was gone (IDE loaded).
The CPU core temperatures shown by sensors / i7z are ok and typically
at about 40-50 C when this slowdown happens, so this doesn't look like
thermal throttling.
Any ideas?
ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: linux-image-4.18.0-10-generic 4.18.0-10.11
ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12
Uname: Linux 4.18.0-10-generic x86_64
ApportVersion: 2.20.10-0ubuntu13
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: pkolaczk 3281 F.... pulseaudio
/dev/snd/pcmC0D0c: pkolaczk 3281 F...m pulseaudio
CurrentDesktop: ubuntu:GNOME
Date: Sun Oct 14 22:16:50 2018
DistributionChannelDescriptor:
# This is a distribution channel descriptor
# For more information see
http://wiki.ubuntu.com/DistributionChannelDescriptor
canonical-oem-somerville-xenial-amd64-20160624-2
HibernationDevice: RESUME=UUID=4836842e-0116-43c4-98b4-7a56427f81f1
InstallationDate: Installed on 2017-04-12 (549 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary
20160624-10:47
MachineType: Dell Inc. Precision 5520
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=pl_PL.UTF-8
SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.18.0-10-generic
root=UUID=7f76b1f0-8fef-41cc-86a2-99e554cb4d40 ro acpi_rev_override quiet
splash iwlwifi.power_save=1 crashkernel=384M-:128M crashkernel=384M-:128M
vt.handoff=1
RelatedPackageVersions:
linux-restricted-modules-4.18.0-10-generic N/A
linux-backports-modules-4.18.0-10-generic N/A
linux-firmware 1.175
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/24/2018
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.11.0
dmi.board.name: 06X96V
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.11.0:bd07/24/2018:svnDellInc.:pnPrecision5520:pvr:rvnDellInc.:rn06X96V:rvrA00:cvnDellInc.:ct10:cvr:
dmi.product.family: Precision
dmi.product.name: Precision 5520
dmi.product.sku: 07BF
dmi.sys.vendor: Dell Inc.
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