Re: [PATCH - resend] Memory-Hotplug: Fix the bug on interface/dev/mem for 64-bit kernel(v1)

[KAMEZAWA Hiroyuki]

On Fri, 08 Jan 2010 20:47:54 +0100
Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:

> H. Peter Anvin wrote:
> > On 01/07/2010 07:32 PM, Zheng, Shaohui wrote:
> >> Resend the patch to the mailing-list, the original patch URL is 
> >> http://patchwork.kernel.org/patch/69075/, it is not accepted without comments,
> >> sent it again to review.
> >>
> >> Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel
> >>
> >> The new added memory can not be access by interface /dev/mem, because we do not
> >>  update the variable high_memory. This patch add a new e820 entry in e820 table,
> >>  and update max_pfn, max_low_pfn and high_memory.
> >>
> >> We add a function update_pfn in file arch/x86/mm/init.c to udpate these
> >>  varibles. Memory hotplug does not make sense on 32-bit kernel, so we did not
> >>  concern it in this function.
> >>
> > 
> > Memory hotplug makes sense on 32-bit kernels, at least in virtual
> > environments.
> 
> No VM currently supports it to my knowledge. They all use traditional
> balooning.
> 
> If someone adds that they can still fix it, but right now fixing it on 64bit
> is the important part.
> 
I wonder...with some modification, memory hotplug (or Mel's page coalescing)
can be used for balloning in MAX_ORDER page size.
I'm sorry if VM' baloon drivers has no fragmentaion problem.

Thanks,
-Kame

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