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(envelope-from waltdnes@waltdnes.org)
Date: Fri, 14 Jun 2024 15:53:04 -0400
From: Walter Dnes <waltdnes@waltdnes.org>
To: gentoo-user@lists.gentoo.org
Subject: Re: [gentoo-user] CPU frequency governors and temperatures
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<10483462.nUPlyArG6x@rogueboard>
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On Fri, Jun 14, 2024 at 11:54:52AM +0100, Michael wrote
> I would think 46-48°C is refreshingly cool, but it very much depends
> on the CPU chip, the MoBo and its BIOS/microcode settings.
I looked up my CPU (see my reply to Dale). The max temp allowed is
71.3 C. A short kernel compile is one thing. I tried schedutil during
an emerge world update, and the temp was hitting 70 C. Ouch! schedutil
has to go.
> I recall an early i7 CPU laptop would not go above 2,400MHz when
> 4core/8threads were running, but on single core processes I would
> see it on i7z jumping up to 4,200MHz.
Speaking of cores+threads... I had always thought my cpu had 12
cores. i.e. /proc/cpuinfo showed 12 "cpus" as did directory
/sys/devices/system/cpu/ But I was wrong. The specs show 6 real cores,
plus hyperthreading. See Greg Kroah-Hartman's presentation about the
security issue called "hyperthreading"...
https://events19.linuxfoundation.org/wp-content/uploads/2018/07/gregkh_mds.pdf
Read it and weep. Page 6 summarizes it succinctly...
==================================================
OpenBSD was right
* Guessed more problems would be in this area
* Disabled SMT for Intel chips in June 2018
* Repeated the plea to disable this in August 2018
* Prevented almost all MDS issues automatically
* Security over performance
* Huge respect!
==================================================
I immediately went into the BIOS and disabled hyperthreading... and
adjusted makeopts in make.conf <G>
> What do you get when you run make with '-j jobs', where jobs=max
> threads of your CPU?
I hadn't realized that this applied to kernel compiling as well as
portage "emerge". Since my system now shows 6 (real) cores, I set 5
jobs. My /usr/src/makeover script is now...
===========================================================
#!/bin/bash
make -j 5 && \
make modules_install && \
cp arch/x86_64/boot/bzImage /boot/vmlinuz-experimental && \
cp System.map /boot/System.map-experimental && \
cp .config /boot/config-experimental
===========================================================
Since I wanted to exorcise schedutil from my system, I had an excuse
to run another compile. From /usr/src/linux I executed...
cp .config ..
make mrproper
cp ../.config .
time ../makeover
I had manually selected "userspace" and 2900000 khz. The result was
so farcical, I repeated it a second time to confirm it was for real.
real 4m43.120s
user 20m11.003s
sys 1m25.728s.
Under 5 minutes. Like wow! The CPU stayed pegged at around 2.900 Ghz
and the temperature never got over 47 C. Thank you very much for that
info about jobs for make.
--
Roses are red
Roses are blue
Depending on their velocity
Relative to you