Re: strange policy loading problem

[Eric Paris <eparis@redhat.com>]

On Thu, 2010-03-11 at 14:16 -0500, Stephen Smalley wrote:
> On Wed, 2010-03-03 at 10:18 +1100, Russell Coker wrote:
> > I'm running a 2.6.32 system under KVM and it keeps OOMing when I try to run 
> > semodule.
> > 
> > # free
> >              total       used       free     shared    buffers     cached
> > Mem:        507532     475320      32212          0       4168      11148
> > -/+ buffers/cache:     460004      47528
> > Swap:       524280      19848     504432
> > 
> > The policy.24 file is just under 900K in size, the output of free is above, it 
> > doesn't seem particularly short of RAM.  The dmesg output is below.  Any 
> > suggestions for what I should investigate?
> > 
> > I could just give the VM a gig of RAM, but I run lots of real systems with 
> > less than 512M so I would like this to work.
> > 
> > 
> > [10750.523296] load_policy: page allocation failure. order:4, mode:0xc0d0
> > [10750.524503] Pid: 13383, comm: load_policy Not tainted 2.6.32-trunk-amd64 #1
> 
> This has been reproduced by others, and in looking further at it, I
> think it is due to switching the avtab from using vmalloc() to using
> kmalloc() as part of commit 3232c110b56bd01c5f0fdfd16b4d695f2e05b0a9
> without reducing MAX_AVTAB_SIZE sufficiently to ensure that we don't put
> too much pressure on the slab allocator.  Options seem to be:
> 1) Reduce MAX_AVTAB_SIZE further so that the max avtab allocation is a
> lower order allocation that isn't likely to fail on kcalloc, and keep
> using that always.
> 2) Change the avtab code to dynamically select use of vmalloc/vfree or
> kcalloc/kfree depending on the selected avtab size.

lib/flex_array.c also looks like it could be a solution.  Probably the
best solution since we don't have to worry about future changes and
people forgetting about the limitation and reasons for either 1 or 2.

-Eric
> 



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