OT: High CPU on Linux?

Sep 21, 2018 13 Replies
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Theo

I've had that when a driver for an nvidia GPU is installed, but no GPU is present. Try uninstalling any package with 'nvidia' in the name. Otherwise google 'systemd udevd cpu' and there's a bunch of postings about it - can be different causes. Theo

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T

Just in case this is one of those 'known things' and to save be wasting time on re-inventing the wheel ...



I picked up a second hand Dell Inspiron 1525 Laptop for my mate (from another mate with a PC shop) to 'evaluate' (the viability of a laptop for him and Linux as an OS) and stuck Mint MATE on it. All seemed ok till the other day the screen died (looks like the CFL inverter). We swapped it for a 1545 and just transferred the Linux SSD over and whilst it booted and worked, it seemed to be labouring and upon running System Monitor, I saw near 100% CPU utilisation (both cores).



I took it away anyway, updated the BIOS from A10 to 14 (in case it made a difference) and then swapped the drive out for the freshly installed W10 that was in the 1525, and after a wodge of updates, that seems to be running as expected (background CPU low)?



Thinking it might be tat I just swapped the drive over, I downloaded, burned and booted from a fresh Mint 19 64 Cinnamon DVD and checked system monitor and it's exactly the same on that? ;-(



A quick Google suggests there may have been a bug or some such that can cause this sort of issue for Linux but I didn't easily stumble on any simple / cure.



Now, whilst it would be very easy to give him this alternate laptop running W10, part of the exercise was to see if he could use Linux as I feel that could be better / safer for him for when just checking emails, browsing the web and Facebook ... and he seemed happy with it for that for the 2 weeks he had it.



But ... now he's got the Synology NAS ... might he be better off with W10 as 1) he know Windows better than he knows Linux (as do I re helping him) and if he runs Windows, 2) might it be easier to run regular backups to the NAS (if he buys a family licence of Macrium Reflect etc)?



I'd like to see if there was a fix for this CPU / Linux issue first as then we have more options.



Running Top suggests that currently, the CPU is 98.7% dedicated to systemd-udevd?



Cheers, T i m



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T

I've had that when a driver for an nvidia GPU is installed, but no GPU is present. Try uninstalling any package with 'nvidia' in the name.

Otherwise google 'systemd udevd cpu' and there's a bunch of postings about it - can be different causes.

Theo

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T

I'll check that out later Theo but would it be likely to be trying to run such a driver from a Live DVD?

Ok, thanks.

Isn't udev to do with the handling of hot-plug devices and the like ... as if so, I was wondering if there was something wrong with the laptop hardware, if it was generating loads of spurious interrupts or some such? Even if it was the case I'm not sure why W10 wouldn't suffer the same issue but as we know, Linux isn't Windows. ;-)

Cheers, T i m

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T

There are 2 trivial fixes.

  1. shut down systemd-udevd & see if it's ok
  2. Stick a different linux in. Obviously one can also google to find fixes usually

NT

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M

Is Bluetooth disabled in the BIOS ?

michael adams

...

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T

It is, but I think it's a bug provoked by moving the HDD from one machine to another. Something was configured for the previous hardware, which isn't there any more, and so it's stuck in a loop going 'hello, can you hear me now?'. Or something along those lines.

This bug report, which mentions your laptop, suggests it could be Bluetooth related:

formatting link
and suggests disabiling Bluetooth in BIOS, or installing an older kernel package like 4.13.

Theo

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T

Yes, I get the theory Theo but why would it then suffer the exact same issues when booting from a live DVD?

Which is exactly what I just did (with the straight swapped drive [1]) and all is now quiet in the glen. ;-)

So, I'll leave him with (just) Linux for now and see if he appreciates the faster (dual core) machine.

Luckily, I don't think he uses BT for anything ...

Cheers, T i m

[1] I did find one and fairly innocuous reference to nvidia in Synaptic and removed it but it didn't make any difference.
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T

That are required to fix a know bug that has been around for some time?

THat doesn't seem that trivial and I can't see a button for that on the keyboard on in the menus. ;-)

That could well have the same kernel or could end up getting upgraded to the same kernel later on?

And Luckily I have, by disabling some of the hardware, hardware that works perfectly well under Windows? [1]

Luckily I don;t think he uses bluetooth ...

Cheers, T i m

[1] Unsurprisingly of course, given all the hardware was 'Designed for Windows'. ;-)
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T

It is now. ;-)

Do we know *why* something as trivial as the presence of a bluetooth module should kill a machine so?

Cheers, T i m

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T

It shouldn't do. It's apparently a bug in kernel 4.15 - it's fixed in 4.16.

Theo

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T

Well quite. ;-)

4.15.0-34-generic x86_64

So, according to the Update Manager the laptop is up to date so will / should 4.16 come though automatically at some time Theo (I've turned automatic updates on [1]).

Cheers, T i m

[1] This (automatic updates (via a gui option)) has been something I have been hoping for on Linux for *years* and the reason it was said not to be available was because the Linux geeks insisted that 1) everone *would* update their machines manually (wrong) and so that there was no need for automatic updates (wrong) and that everone would want to 'vet' what updates they were applying (wrong). Once again this was a demonstration just how out of touch with 'real users' some Linux geeks were (are)? ;-)
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T

Prolly cos the driver can't cope with something in your hardware and is not failing gracefully

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T

So does this 'driver' exist in the kernel as it seems it's been fixed in a later one?

And when you say driver, they seem to call it 'a bug'? ;-)

So, Mint was running fine in a Dell Inspiron 1525 laptop. One of the 'plusses' for Linux over Windows is that you are supposed to be able to take a hdd out of one machine and put it in another and it will work (whereas Windows won't, according to the Linux geeks).

So, that's what I did but it shouldn't have been much of a stretch for it as it was going back into a Dell Inspiron 15** laptop. It worked but it was obviously an accident waiting to happen, because of a bug in the kernel.

In contrast (ironically) the W10 that was originally in the 1525 worked perfectly in the 1545, so basically the opposite of what many Linux geeks say.

Now, I know that that isn't typical ... I know that there is more chance of a Linux install from one machine working in another than it would be for Windows (worse with some versions over others) but, once again I've spent more time trying to get Linux to just work how it should than I have Windows on the same hardware.

I'm not surprised of course because Windows was 'designed' for that hardware whereas in many cases the only way the hardware is supported under Linux is because of the best efforts of men in sheds and from reverse engineering the Windows drivers.

Anyway, all seems good now and I'll try re-enabling the bluetooth module when the new kernel is released.

The system 'snapshot' feature looks interesting, especially if it works and if he can put it on his NAS. ;-)

Cheers, T i m

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J

Not to mention the point that countless linux installs don't have users.

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