Temperatures:
Before the performance drop: up to 97 C
After performance drop: 52-55 C
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https://bugs.launchpad.net/bugs/1797802
Title:
Erratic behavior of intel pstate CPU frequency cont
I collected some perf data for further analysis.
I run a simple arithmetic multi-core benchmark.
The benchmark is 100% CPU bound - it adds 2 integers.
perf record java -jar target/benchmarks.jar
org.ttnr.pmato.e2.cpumem.ArithmeticsBenchmark.add -wi 0 -i 40 -t 4 -f 1
# JMH version: 1.21
# VM vers
Perf data collected for the run above.
** Attachment added: "perf.data"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1797802/+attachment/5203562/+files/perf.data
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More observations:
The problem does not happen if I disable Intel speed-step in BIOS.
In this case, the CPU frequency of all cores goes to 2998 MHz whenever under
load, and stays stable regardless of how long the load is applied.
The problem still happens even if intel_pstate=disable is passed
** Changed in: linux (Ubuntu)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu)
Status: Confirmed => Incomplete
** Changed in: linux (Ubuntu)
Status: Incomplete => Triaged
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** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
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https://bugs.launchpad.net/bugs/1797802
Title:
Erratic behavior of intel pstate CPU frequency control
To manage no
And as soon as I hit "rebuild project" in the IDE, the frequencies go
immediately down from 2.8 GHz to about 1.2-1.5 GHz now.
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Title:
Erratic beh
Huh, another surprise. After running my infinte loop for the time I
wrote the previous post, suddenly it "magically" fixed itself and now
one core reports 100% C0 and ~6% C1, temperature 57, voltage 0.94. The
frequency did not go above 2.8 GHz, though.
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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
Is it normal that C-states percentages reported by i7z don't sum up to 100%,
but exceed it?
Under load, I frequently get C0% close to 99%, but at the same time Halt is at
about 40-60%.
Also when C0 is >90, the frequency of cores goes DOWN. This looks totally
reversed to me.
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Update: I got the "package temperature above threshold" again (still
using 4.18.0-10 kernel), but it did not cause visible performance loss
and i7z still shows the CPU freq can go up to ~3.8 GHz easily. So maybe
these messages are not related.
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> Did this issue start happening after an update/upgrade? Was there a
prior kernel version where you were not having this particular problem?
It started happening after upgrading from 18.04 to 18.10.
> Would it be possible for you to test the latest upstream kernel? Refer
to https://wiki.ubuntu.c
Aaaah, I can see plenty of this in syslog:
Oct 14 22:30:59 p5520 kernel: [ 9481.033687] CPU3: Package temperature above
threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033688] CPU7: Package temperature above
threshold, cpu clock throttled (total events =
BTW, when the system is in this weird state, CPU fans are running at the
lowest speed (but running) and never go to their max speed, even under
heavy CPU load like compiling stuff.
Is there a hidden energy saving thing that tries to keep my CPU clock
low / voltages low at high load?
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You recei
Did this issue start happening after an update/upgrade? Was there a
prior kernel version where you were not having this particular problem?
Would it be possible for you to test the latest upstream kernel? Refer
to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest
v4.19 kernel[0
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