Re: [RFC] Tight check of pfn_valid on sparsemem

[Minchan Kim <minchan.kim@gmail.com>]

Hi, Dave. 

On Tue, Jul 13, 2010 at 09:35:33AM -0700, Dave Hansen wrote:
> On Wed, 2010-07-14 at 00:43 +0900, Minchan Kim wrote:
> > 3 is not a big deal than 2 about memory usage.
> > If the system use memory space fully(MAX_PHYSMEM_BITS 31), it just consumes
> > 1024(128 * 8) byte. So now I think best solution is 2. 
> > 
> > Russell. What do you think about it? 
> 
> I'm not Russell, but I'll tell you what I think. :)
> 

No problem. :)

> Make the sections 16MB.  You suggestion to add the start/end pfns

I hope so. 

> _doubles_ the size of the structure, and its size overhead.  We have
> systems with a pretty tremendous amount of memory with 16MB sections.

Yes. it does in several GB server system.

> 
> If you _really_ can't make the section size smaller, and the vast
> majority of the sections are fully populated, you could hack something
> in.  We could, for instance, have a global list that's mostly readonly
> which tells you which sections need to be have their sizes closely
> inspected.  That would work OK if, for instance, you only needed to
> check a couple of memory sections in the system.  It'll start to suck if
> you made the lists very long.

Thanks for advise. As I say, I hope Russell accept 16M section. 

> 
> -- Dave
> 

-- 
Kind regards,
Minchan Kim