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

[David T. Lewis]

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