Re: [dm-crypt] system freezes when using swap that is encrypted

[Carlo Wood <carlo@alinoe.com>]

Hi all!

I've been a member of this list for a long long time, and
what-do-you-know, I finally see something that I can respond to :)

I have the following problem for a long time now: whenever my
system uses all memory (and would start to use swap) it freezes.
I can't even remote login anymore - although there remains a
desktop image on the monitor. Only possible option is to reboot.

I use the following configuration for my swap:

/etc/fstab:

/dev/mapper/cswap none          swap    sw,pri=1        0       0


/etc/crypttab:

cswap       /dev/md1        /dev/random swap


/dev/md1 is a 16 GB partition on my RAID 5 with three disks.

Could this be related?

On Sat, Nov 13, 2010 at 11:49:53AM -0700, Nicolas Bock wrote:
> The interesting thing is though that when I make the 2 swap partitions
> regular swap, i.e. not encrypted, then the same program does not get
> OOM killed and the system stays responsive all the way to the end of
> allocating the 10GB. So it's not a problem of memory pressure, it's
> rather related to the fact that the swap is encrypted.
> 
> nick
> 
> On Sat, Nov 13, 2010 at 07:53, Arno Wagner <arno@wagner.name> wrote:
> > On Fri, Nov 12, 2010 at 08:40:43PM -0700, Nicolas Bock wrote:
> >> I think I have ruled out now that this is a hard crash. I have 8GB of
> >> physical memory and another 8GB as swap. I allocated 10GB in a C
> >> program and after it had written to about  7GB or so, the system
> >> froze. But after maybe 20 minutes the system got unstuck and had
> >> killed the job. Since I am on amd64, I am not sure why the job got
> >> killed, it should certainly have had enough memory to write to.
> >
> > I don't know what criteria lead to activation of the OOM killer,
> > but I use one application that allocates up to 150 MB of memory,
> > but never uses (accesses) it. This app runs fine in a qemu
> > with 16MB RAM and 200MB swap. It is possible that your process
> > gets killed, if it uses more memory than the larger of swap
> > and main memory.
> >
> > Arno
> >
> >
> > --
> > Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@wagner.name
> > GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
> > ----
> > Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
> >
> > If it's in the news, don't worry about it.  The very definition of
> > "news" is "something that hardly ever happens." -- Bruce Schneier

-- 
Carlo Wood <carlo@alinoe.com>