Re: writepage return value check in vmscan.c

[Andrea Arcangeli <andrea@suse.de>]

On Thu, Oct 24, 2002 at 12:15:32PM -0700, chrisl@vmware.com wrote:
> Yes, but even now days it will able to lockup machine by doing that.
> 
> Try the test bigmm program I attach to this mail. It will simulate vmware's
> memory mapping. It can easily lockup the machine even though there is
> enough disk space.
> 
> See the comment at the source for parameter. basically, if you want
> 3 virtual machine, each have 2 process, using 1 G ram each you can do:
> 
> bigmm -i 3 -t 2 -c 1024
> 
> I run it on two 4G and 8G smp machine. Both can dead lock if I mmap
> enough memory.

I run the above command on my laptop with 256M of ram and 1G of swap
with kde running (though idle) and the task was correctly killed:

Oct 24 22:29:32 x30 kernel: VM: killing process bigmm

the machine never deadlocked. Probably it's one of the oom deadlocks
that I fixed in my 2.4 -aa tree and that the oom killer heuristic in
mainline cannot figure out. Please try to reproduce with 2.4.20pre11aa1.
thanks.

> Prepare to reset the machine if you try that, you have been warned :-)

If you're running an oom deadlock prone kernel.

> > to discard those pages and invaliding those posted writes. At least
> > until a true solution will be available you should change vmware to
> > preallocate the file, then it will work fine because you will catch the
> > ENOSPC error during the preallocation. If you work on shmfs that will be
> > very quick indeed.
> 
> Yes, shmfs seems to be the only choice so far.

Agreed.

Andrea