What's soft lockup?

[Robert Heller]

At Sun, 5 Jul 2020 08:16:48 +0100 "Ubuntu user technical support,  not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:

> 
> On Sun, 5 Jul 2020 at 05:55, 孙世龙 sunshilong <sunshilong369 at gmail.com> wrote:
> >
> > Hi,
> >
> > As the subject, how can detect the soft lockup?
> 
> What do you mean by a soft lockup?

I expect that the "soft lockup" the OP is refering to is some sort of memory 
leak related problem and the system goes into serious paging.  Some program is 
gobbling virtual memory and uses up physical RAM and the system starts paging 
everything else out, causing everything to grind to a halt, but without 
actually crashing.  With a large enough swap space and a slow enough "leak" 
the system will continue to run, just very slowly and will probably be very 
unresponsive, but not totally "hung".  If it is not an actual memory leak, but 
just a memory hog, the system will often recover once the memory hog finishes. 
It could also be caused by opening too many windows/tabs in Firefox or Chrome 
or opening too many documents with LibreOffice, or opening a ginormous image 
with gimp, or doing a huge compile or link (including buiding a large Arduino 
"sketch" (for a 32-bit MCU) on a Raspberry Pi 2 with the Arduino up and 
running at the same time -- been there, done that).

The only really "cure" is patience (the system will eventualy recover,
hopefull with out resorting to the oom killer) or else avoiding the problem (I
now use the Arduino CLI build command [arduino-build] and don't bother to fire
up the IDE for the larger sketches [*I* don't actually use the IDE's code
editor anyway]). 

> 
> Colin
> 

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