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Hamlet
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Joined: 15 Apr 2005
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PostPosted: Sun Jul 24, 2016 9:10 pm    Post subject: Overheating processor floods console with null characters Reply with quote

At least, that's how it looks like.

I am installing Gentoo -- text mode here -- on Apple hardware ("MacBookPro11,5"), and when compiling in full power fan becomes very loud.
So far, it's "normal": I have observed the same in OSX and on others' similar laptops as well.
On Linux, though, very soon a bunch of Machine Check Exceptions is emitted, about temperature and throttling.
Roughly at the same time, the console behaves weirdly, and it looks like something is injecting (null?) characters in it.
That's of little consequence in bash, since readline (or whatever) does a good job of ignoring them.
But it becomes troublesome in programs like vim, at the point that it is hard to quit them because the command becomes ":^@^@q^@^@^@" or so. Even a tmux window change becomes a challenge (^B b).
These characters seem to follow the same path as the MCE warnings above, that is, they are emitted in whichever console is active. I could suppress MCE output increasing the printk threshold (`man 2 sysctl`), but these other characters seem unstoppable.
For example, while compilation is ongoing (as administrator), if I go to another virtual console and as a normal user start a session and type `cat`, I can see the screen progressively filling with "^@" (that are in my recollection representations of a null character), at a irregular rate of a few per second. Between emerges, the fan subsides and so do the "^@".
I don't see any of this from a remote terminal (connected through SSH).

I don't even know where to start to tackle this problem. That makes text console mostly unusable while CPUs are seriously busy.
Suggestions?
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Hu
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PostPosted: Sun Jul 24, 2016 10:34 pm    Post subject: Reply with quote

Start by taking steps to prevent overheating. I am not aware of any MCE events where it is acceptable for them to occur on a properly functioning system. If you are getting MCE events, you have a problem. It may be a treatable problem such as insufficient cooling, rather than an irreparable hardware fault.
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ct85711
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PostPosted: Mon Jul 25, 2016 12:38 am    Post subject: Reply with quote

As Hu mentioned, how your console is operating is secondary to your main issue, and the most critical one.

Your system should never be overheating ever. Just ignoring this can and potentially will cause damage to your system (more than what may have already happened). The longer you ignore this, the higher chance damage may occur to the system to the point that it'll turn into a very expensive paper weight.
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C5ace
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Joined: 23 Dec 2013
Posts: 277
Location: Brisbane, Australia

PostPosted: Mon Jul 25, 2016 12:55 pm    Post subject: Re: Overheating processor floods console with null character Reply with quote

Hamlet wrote:
At least, that's how it looks like.

I am installing Gentoo -- text mode here -- on Apple hardware ("MacBookPro11,5"), and when compiling in full power fan becomes very loud.
So far, it's "normal": I have observed the same in OSX and on others' similar laptops as well.
On Linux, though, very soon a bunch of Machine Check Exceptions is emitted, about temperature and throttling.
Roughly at the same time, the console behaves weirdly, and it looks like something is injecting (null?) characters in it.
That's of little consequence in bash, since readline (or whatever) does a good job of ignoring them.
But it becomes troublesome in programs like vim, at the point that it is hard to quit them because the command becomes ":^@^@q^@^@^@" or so. Even a tmux window change becomes a challenge (^B b).
These characters seem to follow the same path as the MCE warnings above, that is, they are emitted in whichever console is active. I could suppress MCE output increasing the printk threshold (`man 2 sysctl`), but these other characters seem unstoppable.
For example, while compilation is ongoing (as administrator), if I go to another virtual console and as a normal user start a session and type `cat`, I can see the screen progressively filling with "^@" (that are in my recollection representations of a null character), at a irregular rate of a few per second. Between emerges, the fan subsides and so do the "^@".
I don't see any of this from a remote terminal (connected through SSH).

I don't even know where to start to tackle this problem. That makes text console mostly unusable while CPUs are seriously busy.
Suggestions?


Had a similar problem when installing Gentoo in Queensland, Australia outback summer with +45C temperature on a laptop. Solution: placed the laptop into a freezer and do a remote install from a desktop through ssh.
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frostschutz
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PostPosted: Mon Jul 25, 2016 2:05 pm    Post subject: Re: Overheating processor floods console with null character Reply with quote

C5ace wrote:
Solution: placed the laptop into a freezer and do a remote install from a desktop through ssh.


A fridge is usually too humid for electronics. Also fridge only cools passive things down over time. If you put a laptop inside that actively produces heat then the fridge has to use lots of watts to cool down, and it might not manage to. So at best this only works short term...

Just give it more airflow.
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C5ace
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Location: Brisbane, Australia

PostPosted: Mon Jul 25, 2016 11:33 pm    Post subject: Re: Overheating processor floods console with null character Reply with quote

frostschutz wrote:
C5ace wrote:
Solution: placed the laptop into a freezer and do a remote install from a desktop through ssh.


A fridge is usually too humid for electronics. Also fridge only cools passive things down over time. If you put a laptop inside that actively produces heat then the fridge has to use lots of watts to cool down, and it might not manage to. So at best this only works short term...

Just give it more airflow.


It works because the air inside a deep freezer is -18C and extremely dry. The thermal load was only for a few hours during the installation.
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Ant P.
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PostPosted: Tue Jul 26, 2016 3:46 am    Post subject: Reply with quote

Those are input events coming from the ACPI drivers. There may be a way to disable those, but the simplest one is just to run X.
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c00l.wave
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PostPosted: Thu Jul 28, 2016 10:27 pm    Post subject: Re: Overheating processor floods console with null character Reply with quote

Hamlet wrote:
when compiling in full power fan becomes very loud.

At least automatic fan speed control seems to have been implemented somewhere, finally... (in earlier MacBooks this had to be done in software, the hardware would not mind updating fan speeds by temperature at all)

Quote:
On Linux, though, very soon a bunch of Machine Check Exceptions is emitted, about temperature and throttling.

... but that makes it look pretty faulty, then. Again!

Personally, I've given up installing Linux on notebooks and Mac hardware in particular after I managed to supposedly desolder or otherwise permanently fail the graphics chipset by even slightly overheating my 2008-series MacBookPro (the one with the bad GPU solder joints as the mandatory glitch every Apple computer got so far). There were no MCE messages at that point, so I guess it may have been regarded as much more "in spec" as your scenario. I don't know if Linux on mobile hardware other than Macs works okay these days (not counting Android etc. although they have some horrid bugs as well) but Apple demonstrates quite nicely that - despite a lot of people working with those machines - there's still hardware that just doesn't seem to take Linux in a usable, non-destructive way.

Some words of advice (although plenty people may not want to hear it): Save yourself some money and a lot of trouble and if you can't manage to fix the overheating issues immediately, stay with OS X and Windows. Don't attempt to continue with Linux unless that notebook appears to run in a sane state or you risk loosing it. On a desktop you can always swap broken components easily and (usually) cheap, on a notebook you can't (especially true for Apple computers of all kinds these days). So choose wisely if running Linux on it is worth the money, especially if the hardware is still as young (and sellable to replace with a more compatible notebook) as yours.
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