On Sun, 18 Jul 2010 19:18:31 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > Kukjin reported oops happen while he change min_free_kbytes > http://www.spinics.net/lists/arm-kernel/msg92894.html > It happen by memory map on sparsemem. > > The system has a memory map following as. > section 0 section 1 section 2 > 0x20000000-0x25000000, 0x40000000-0x50000000, 0x50000000-0x58000000 > SECTION_SIZE_BITS 28(256M) > > It means section 0 is an incompletely filled section. > Nontheless, current pfn_valid of sparsemem checks pfn loosely. > It checks only mem_section's validation but ARM can free mem_map on hole > to save memory space. So in above case, pfn on 0x25000000 can pass pfn_valid's > validation check. It's not what we want. > > We can match section size to smallest valid size.(ex, above case, 16M) > But Russell doesn't like it due to mem_section's memory overhead with different > configuration(ex, 512K section). > > I tried to add valid pfn range in mem_section but everyone doesn't like it > due to size overhead. This patch is suggested by KAMEZAWA-san. > I just fixed compile error and change some naming. > > This patch registers address of mem_section to memmap itself's page struct's > pg->private field. This means the page is used for memmap of the section. > Otherwise, the page is used for other purpose and memmap has a hole. > > This patch is based on mmotm-2010-07-01-12-19. > > Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Reported-by: Kukjin Kim <kgene.kim@xxxxxxxxxxx> Thank you for working on this. I myself like this solution. I think ARM guys can make this default later (after rc period ?) Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>