Re: [PATCH 3/7] Generic Virtual Memmap support for SPARSEMEM

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 13 Jul 2007 16:17:32 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:

> > Note
> > >From memory hotplug development/enhancement view, I have following thinking now.
> >  
> >  1. memmap's section is *not* aligned to "big page size". We have to take care
> >     of this at adding support for memory_hotplug/unplug.
> 
> You can call the functions for virtual memmap allocation directly. They 
> are already generic and will call the page allocator instead of the 
> bootmem allocator if the system is already. They will give you the 
> properly aligned memory. Perhaps you can just change a few lines 
> in sparse_add_one_section to call the vmemmap functions instead?
> 
yes, I think so now. But we'll see warnings of "section mismatch".
Because this patch includes following.

==
func() {
	if()
		call_generic_func
	else
		call_boot_func.
}
==



> >  2. With an appropriate patch, we can allocate new section's memmap from
> >     itself. This will reduce possibility of memory hotplug failure becasue of
> >     large size kmalloc/vmalloc. And it guarantees locality of memmap.
> >     But maybe need some amount of work for implementing this in clean way.
> >     This will depend on vmemmap.
> 
> That is a good idea. Maybe do the simple approach first and then the other 
> one?
Yes, simple first. Above one will be an option for people who use 
big-section-size, like ia64.

-Kame

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