The "Hertzbleed" vulnerability

Posted Jun 14, 2022 20:54 UTC (Tue) by flussence (guest, #85566)
Parent article: The "Hertzbleed" vulnerability

> You can prevent Hertzbleed by disabling frequency boost.

Oh, nothing to worry about then. I do that already because I've never seen a single measurable benefit from it on a Ryzen and it only increases peak CPU temps by 20°C. Highly recommend others give it a try, regardless of this week's alarmism.

Put `printf 0 >| /sys/devices/system/cpu/cpufreq/boost` in your startup scripts, or do the equivalent in a udev rule if you want to be fancy. Simple.

The "Hertzbleed" vulnerability

Posted Jun 14, 2022 22:15 UTC (Tue) by bartoc (guest, #124262) [Link] (2 responses)

On a desktop it doesn't really matter, but on a laptop it absolutely does. Also, 20C is quite a lot, that would make my fans somewhat more noisy (although already they are annoying because ryzen tends to fluctuate around in temperature a lot, so they throttle up for a very short amount of time before throttling back down, this is really an issue with the motherboard firmware though).

How much does this increase power usage? Like this sort of thing matters the most for servers/multitenant machines, and those definitely do want scaling.

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 9:26 UTC (Wed) by eduperez (guest, #11232) [Link] (1 responses)

What @flussence is trying to say, is that *enabling* "frequency boost" increases the temperatures by 20C, and has no noticeable benefits on performance; thus, he is advocating to *disable* it. Also, notice that "frequency boost" is about (temporarily) running the CPU at a frequency higher than the baseline frequency; perhaps you where thinking about "frequency scaling", where CPU runs at a lower frequency, during periods of low load.

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 19:21 UTC (Wed) by bartoc (guest, #124262) [Link]

I was indeed!

Comment fully retracted :)

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 0:41 UTC (Wed) by jmclnx (guest, #72456) [Link]

For me it was

echo "1" > /sys/devices/system/cpu/intel_pstate/no_turbo

and no performance issues for me on a Laptop

I found that in the link below, interesting it is from 2019, but since I found out gamers do that in order to do something else to max their CPU out.

https://sleeplessbeastie.eu/2019/07/15/how-to-disable-int...

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 1:04 UTC (Wed) by ccchips (subscriber, #3222) [Link] (3 responses)

I have Intel NUC 10, on Linux Mint 20. Where would I find that switch? There's no entry matching the one in your message. When I try to run your command as sudo, I get "Permission Denied."

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 5:00 UTC (Wed) by devnull13 (subscriber, #18626) [Link]

Does this answer your question? https://forums.linuxmint.com/viewtopic.php?t=355295

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 18:12 UTC (Wed) by flussence (guest, #85566) [Link]

I was under the impression that was the standard sysfs knob for it, but as others have pointed out, Intel does its own thing.

The "Hertzbleed" vulnerability

Posted Jun 24, 2022 3:05 UTC (Fri) by danielwagenaar (guest, #14814) [Link]

If you run

sudo echo 1 > /sys/whatever

only the "echo 1" is run as root. The piping to "/sys/whatever" is done by your shell using your regular user account. Hence the idiom

echo 1 | sudo tee /sys/whatever

which runs the "echo 1" under your regular user account, and lets the "tee" command copy the output out to "/sys/whatever" as root.

Hope that helps.

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 14:34 UTC (Wed) by nye (subscriber, #51576) [Link] (2 responses)

> I do that already because I've never seen a single measurable benefit from it on a Ryzen and it only increases peak CPU temps by 20°C

If you can't measure a performance difference, you have something very wrong with one or more of your hardware, BIOS, and/or kernel - you should generally be seeing around 30% depending on the specific CPU.

I'd say maybe it's just not working at all, but that wouldn't explain the heat increase so there must be something more going on, eg you have bad hardware and it's increasing the voltage a huge amount in order to get a tiny boost. I had a 3700x which was absolute garbage so AMD is definitely producing some bad silicon, but even then the speed difference was meaningful; it's just that the temperature increase was wildly non-linear.

The "Hertzbleed" vulnerability

Posted Jun 15, 2022 18:10 UTC (Wed) by flussence (guest, #85566) [Link] (1 responses)

BIOS most certainly kicks rocks - it's a Gigabyte board. The normal max clock is 3800 without boost and something like 4400 with, but leaving it turned on doesn't improve life in any way for me while the downsides are immediately visible. If it's dud silicon then I can accept that, but I'd at least like it to last long enough to replace with a Linux-running M2 down the line :-)

The "Hertzbleed" vulnerability

Posted Jun 20, 2022 15:58 UTC (Mon) by eduperez (guest, #11232) [Link]

Going from 3800GHz to 4400GHz is a 16% increase, but only in CPU frequency, among a myriad of other factors that affect performance... it's probably imperceptible for many use cases, and not worth the cost.