Re: Memory exhaustion testing?

[Jesper Dangaard Brouer <brouer@redhat.com>]

On Thu, 19 Nov 2015 12:40:50 -0800 (PST)
David Rientjes <rientjes@google.com> wrote:

> On Tue, 17 Nov 2015, Jesper Dangaard Brouer wrote:
> 
> > I did manage to provoke/test the error path in kmem_cache_alloc_bulk(),
> > by using fault-injection framework "fail_page_alloc".
> > 
> > But was a little hard to trigger SLUB errors with this, because SLUB
> > retries after a failure, and second call to alloc_pages() is done with
> > lower order.
> > 
> > If order is lowered to zero, then should_fail_alloc_page() will skip it.
> > And just lowering /sys/kernel/debug/fail_page_alloc/min-order=0 is not
> > feasible as even fork starts to fail.  I managed to work-around this by
> > using "space" setting.
> > 
> > Created a script to ease this tricky invocation:
> >  https://github.com/netoptimizer/prototype-kernel/blob/master/tests/fault-inject/fail01_kmem_cache_alloc_bulk.sh
> > 
> 
> Any chance you could proffer some of your scripts in the form of patches 
> to the tools/testing directory?  Anything that can reliably trigger rarely 
> executed code is always useful.

Perhaps that is a good idea.

I think should move the directory location in my git-repo
prototype-kernel[1] to reflect this directory layout, like I do with
real kernel stuff.  And when we are happy with the quality of the
scripts we can "move" it to the kernel.  (Like I did with my pktgen
tests[4], now located in samples/pktgen/).

A question; where should/could we place the kernel module
slab_bulk_test04_exhaust_mem[1] that my fail01 script depends on?


BTW, I've also added a script for testing NULL handling in normal
kmem_cache_alloc() call see[3].

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer

[1] https://github.com/netoptimizer/prototype-kernel/

[2] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/slab_bulk_test04_exhaust_mem.c

[3] https://github.com/netoptimizer/prototype-kernel/blob/master/tests/fault-inject/fail02_kmem_cache_alloc.sh

[4] https://github.com/netoptimizer/network-testing/tree/master/pktgen

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