Re: Need some help in understanding sparsemem.

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

On Tue, Jul 6, 2010 at 2:11 PM,  <naren.mehra@gmail.com> wrote:
> Hi,
>
> I am trying to understand the sparsemem implementation in linux for
> NUMA/multiple node systems.
>
> From the available documentation and the sparsemem patches, I am able
> to make out that sparsemem divides memory into different sections and
> if the whole section contains a hole then its marked as invalid
> section and if some pages in a section form a hole then those pages
> are marked reserved. My issue is that this classification, I am not
> able to map it to the code.
>
> e.g. from arch specific code, we call memory_present()  to prepare a
> list of sections in a particular node. but unable to find where
> exactly some sections are marked invalid because they contain a hole.

On ARM's sparsememory,

static void arm_memory_present(struct meminfo *mi)
{
        int i;
        for_each_bank(i, mi) {
                struct membank *bank = &mi->bank[i];
                memory_present(0, bank_pfn_start(bank), bank_pfn_end(bank));
        }
}

It just mark _bank_ which has memory with SECTION_MARKED_PRESENT.
Otherwise, Hole.

>
> Can somebody tell me where in the code are we identifying sections as
> invalid and where we are marking pages as reserved.

Do you mean memmap_init_zone?


-- 
Kind regards,
Minchan Kim

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>