Minchan Kim wrote:
>
> Hello.
>
Hello :-)
> On Mon, Jul 12, 2010 at 5:32 PM, Kukjin Kim <kgene.kim@xxxxxxxxxxx> wrote:
> > Russell,
> >
> > Hi,
> >
> > Kukjin Kim wrote:
> >> Russell wrote:
> >> > So, memory starts at 0x20000000 and finishes at 0x25000000. That's
> > fine.
> >> > That doesn't mean the section size is 16MB.
> >> >
> >> > As I've already said, the section size has _nothing_ what so ever to
do
> >> > with the size of memory, or the granularity of the size of memory.
By
> >> > way of illustration, it is perfectly legal to have a section size of
> >> > 256MB but only have 1MB in a section and this is perfectly legal. So
> >> > sections do not have to be completely filled.
> >> >
> >> Actually, as you know, the hole's area of mem_map is freed from bootmem
if
> > a
> >> section has a hole when initializing sparse memory.
> >>
> >> I identified that a section doesn't need to be a contiguous area of
> > physical
> >> memory when reading your comment with the fact that the mem_map of a
> > section
> >> can be smaller than the size of a section.
> >>
> >> I found, however, the kernel panics when modifying min_free_kbytes file
in
> >> the proc filesystem if a section has a hole.
> >>
> >> While processing the change of min_free_kbytes in the kernel, page
> >> descriptors in a hole of an online section is accessed.
> >
> > As I said, following error happens.
> > It would be helpful to me if any opinions or comments.
> >
>
> Could you test below patch?
> Also, you should select ARCH_HAS_HOLES_MEMORYMODEL in your config.
>
Yes, I did it, and no kernel panic happens :-)
Same test...
[root@Samsung ~]# cat /proc/sys/vm/min_free_kbytes
2736
[root@Samsung ~]# echo "2730" > /proc/sys/vm/min_free_kbytes
[root@Samsung ~]#
[root@Samsung ~]# cat /proc/sys/vm/min_free_kbytes
2730
> @@ -2824,8 +2825,13 @@ static void setup_zone_migrate_reserve(struct zone
> *zone)
> for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
> if (!pfn_valid(pfn))
> continue;
> +
> page = pfn_to_page(pfn);
>
> + /* Watch for unexpected holes punched in the memmap */
> + if (!memmap_valid_within(pfn, page, zone))
> + continue;
> +
> /* Watch out for overlapping nodes */
> if (page_to_nid(page) != zone_to_nid(zone))
> continue;
>
>
>
...Could you please explain about this issue?
Thanks.
Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@xxxxxxxxxxx>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.
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