Re: Kdump issue with percpu_alloc=lpage

Vivek Goyal
2009-11-19T14:34:30Z

On Wed, Nov 18, 2009 at 06:25:14PM +0900, Tejun Heo wrote:
> Hello,
>
> 10/29/2009 06:22 AM, John Blackwood wrote:
> >> Thanks Tejun. percpu_to_phys() makes sense to me also. John, would you
> >> like to post a patch for this.
> >
> > Hi Vivek,
> >
> > I'm probably not really NUMA/vm savy enough to attempt a patch
> > for approval at LKML.
> >
> > But maybe someone else more qualified can take up the cause.
>
> Is this still necessary for the current upstream where lpage allocator
> is gone (but vmalloc mapping is still there)?
>

Hi Tejun,

I did load a kdump kernel on 32-rc7 and it worked fine. But I guess in
this case memory might have come from linearly mapped region.

If the default per cpu allocator can get memory from vmalloc region also, then
I think we will need this function which can map virtual address to
physical address.

Are there multiple allocators now? If yes, what are the command line
options and I can try to use some other allocator and see if I can force
the condition where memory comes from vmalloc region and I observe the
crash.

Once I can reproduce it, I can also send you the fix you suggested.

Thanks
Vivek