> Changelog since v2 > o Change some function names > o Remove mark_memmap_hole in memmap bring up > o Change CONFIG_SPARSEMEM with CONFIG_ARCH_HAS_HOLES_MEMORYMODEL > > I have a plan following as after this patch is acked. > > TODO: > 1) expand pfn_valid to FALTMEM in ARM > I think we can enhance pfn_valid of FLATMEM in ARM. > Now it is doing binary search and it's expesive. > First of all, After we merge this patch, I expand it to FALTMEM of ARM. > > 2) remove memmap_valid_within > We can remove memmap_valid_within by strict pfn_valid's tight check. > > 3) Optimize hole check in sparsemem > In case of spasemem, we can optimize pfn_valid through defining new > flag > like SECTION_HAS_HOLE of hole mem_section. > > == CUT HERE == > > 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-2010-07-19 > > Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Reported-by: Kukjin Kim <kgene.kim@xxxxxxxxxxx> > Cc: Mel Gorman <mel@xxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Russell King <linux@xxxxxxxxxxxxxxxx> > --- > arch/arm/mm/init.c | 4 +++- > include/linux/mmzone.h | 22 +++++++++++++++++++++- > mm/mmzone.c | 34 > ++++++++++++++++++++++++++++++++++ > 5 files changed, 58 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c > index f6a9994..25e2670 100644 > --- a/arch/arm/mm/init.c > +++ b/arch/arm/mm/init.c > @@ -482,8 +482,10 @@ free_memmap(int node, unsigned long start_pfn, > unsigned long end_pfn) > * If there are free pages between these, > * free the section of the memmap array. > */ > - if (pg < pgend) > + if (pg < pgend) { > + mark_invalid_memmap(pg >> PAGE_SHIFT, pgend >> PAGE_SHIFT); > free_bootmem_node(NODE_DATA(node), pg, pgend - pg); > + } > } > > /* > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index b4d109e..a3195bd 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -15,6 +15,7 @@ > #include <linux/seqlock.h> > #include <linux/nodemask.h> > #include <linux/pageblock-flags.h> > +#include <linux/mm_types.h> > #include <generated/bounds.h> > #include <asm/atomic.h> > #include <asm/page.h> > @@ -1049,11 +1050,30 @@ static inline struct mem_section > *__pfn_to_section(unsigned long pfn) > return __nr_to_section(pfn_to_section_nr(pfn)); > } > > +void mark_invalid_memmap(unsigned long start, unsigned long end); > + > +#ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL > +#define MEMMAP_HOLE (0x1UL) > +static inline int memmap_valid(unsigned long pfn) > +{ > + struct page *page = pfn_to_page(pfn); > + struct page *__pg = virt_to_page(page); > + return !(__pg->private & MEMMAP_HOLE); > +} > +#else > +static inline int memmap_valid(unsigned long pfn) > +{ > + return 1; > +} > +#endif > + > static inline int pfn_valid(unsigned long pfn) > { > + struct mem_section *ms; > if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) > return 0; > - return valid_section(__nr_to_section(pfn_to_section_nr(pfn))); > + ms = __nr_to_section(pfn_to_section_nr(pfn)); > + return valid_section(ms) && memmap_valid(pfn); > } > > static inline int pfn_present(unsigned long pfn) > diff --git a/mm/mmzone.c b/mm/mmzone.c > index f5b7d17..7c84e5e 100644 > --- a/mm/mmzone.c > +++ b/mm/mmzone.c > @@ -86,4 +86,38 @@ int memmap_valid_within(unsigned long pfn, > > return 1; > } > + > +/* > + * Fill pg->private on hole memmap with MEMMAP_HOLE. > + * pfn_valid() will check this later. (see include/linux/mmzone.h) > + * Evenry arch should call > + * mark_invalid_memmap(start, end) # for all holes in mem_map. > + * please see usage in ARM. > + */ > +void mark_invalid_memmap(unsigned long start, unsigned long end) > +{ > + struct mem_section *ms; > + unsigned long pos, next; > + struct page *pg; > + void *memmap, *mapend; > + > + for (pos = start; pos < end; pos = next) { > + next = (pos + PAGES_PER_SECTION) & PAGE_SECTION_MASK; > + ms = __pfn_to_section(pos); > + if (!valid_section(ms)) > + continue; > + > + for (memmap = (void*)pfn_to_page(pos), > + /* The last page in section */ > + mapend = pfn_to_page(next-1); > + memmap < mapend; memmap += PAGE_SIZE) { > + pg = virt_to_page(memmap); > + pg->private = MEMMAP_HOLE; > + } > + } > +} > +#else > +void mark_invalid_memmap(unsigned long start, unsigned long end) > +{ > +} > #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */ > -- I don't think this works because if the memmap pages get reused, the corresponding struct page->private could be used by chance in such a way that it has the value of MEMMAP_HOLE. Of course unlikely but possible. And after all the whole point of freeing part of the memmap is that it could be reused. --Mika -- 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