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
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