[Vm-dev] Linux 4.4.7.2357 VM crash under memory pressure

[Bert Freudenberg]

On 20.05.2012, at 19:35, David T. Lewis wrote:

> 
> On Sun, May 20, 2012 at 03:08:20PM +0200, Bert Freudenberg wrote:
>> 
>> Hilaire discovered that his newest DrGeo segfaults on the XO-1. It works fine elsewhere, including the XO-1.5, which has pretty much the same OS.
>> 
>> We narrowed down the problem to the XO-1 having only 256 MB of RAM and no swap space. I can reproduce the crash in a virtual Ubuntu 12 with 768 MB RAM (!) but no swap. Top reports:
>> 
>> Mem:    766204k total,   601588k used,   164616k free,    45624k buffers
>> Swap:        0k total,        0k used,        0k free,   277024k cached
>> 
>> but DrGeo still crashes. Etoys runs fine using the same Squeak VM on the same system (and on XO-1). DrGeo is based on Pharo 1.4, using a closure image. Etoys still is pre-closure. 
>> 
> 
> I recall some recent discussion on the Pharo list about some "strange objects"
> that had entered the image for a period of time. It was something to do with
> a mismatch in the number of instance variable slots. The VM crash is happening
> in a method that is stepping through the fields of an object, so if something
> was out of whack there it might well lead to problems.
> 
> The discussion started here:
> 
>  http://lists.gforge.inria.fr/pipermail/pharo-project/2012-May/064539.html
> 
> It would be worth checking if the DrGeo image might have this issue, in
> case those objects might for some reason be interacting badly with the
> garbage collector.
> 
> Dave

Interesting. However, it's strange that this would manifest only on machines with less memory - shouldn't the VM topple over at the first GC no matter what?

- Bert -