[PATCH] ARM: mm: Regarding section when dealing with meminfo
From: Dave Hansen <hidden>
Date: 2011-01-20 17:22:13
Also in:
linux-mm, linux-samsung-soc, lkml
On Thu, 2011-01-20 at 18:45 +0900, KyongHo Cho wrote:
Sparsemem allows that a bank of memory spans over several adjacent sections if the start address and the end address of the bank belong to different sections. When gathering statictics of physical memory in mem_init() and show_mem(), this possiblity was not considered. This patch guarantees that simple increasing the pointer to page descriptors does not exceed the boundary of a section
...
quoted hunk ↗ jump to hunk
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c index 57c4c5c..6ccecbe 100644 --- a/arch/arm/mm/init.c +++ b/arch/arm/mm/init.c@@ -93,24 +93,38 @@ void show_mem(void) pfn1 = bank_pfn_start(bank); pfn2 = bank_pfn_end(bank); - +#ifndef CONFIG_SPARSEMEM page = pfn_to_page(pfn1); end = pfn_to_page(pfn2 - 1) + 1; - +#else + pfn2--; do { - total++; - if (PageReserved(page)) - reserved++; - else if (PageSwapCache(page)) - cached++; - else if (PageSlab(page)) - slab++; - else if (!page_count(page)) - free++; - else - shared += page_count(page) - 1; - page++; - } while (page < end); + page = pfn_to_page(pfn1); + if (pfn_to_section_nr(pfn1) < pfn_to_section_nr(pfn2)) { + pfn1 += PAGES_PER_SECTION; + pfn1 &= PAGE_SECTION_MASK; + } else { + pfn1 = pfn2; + } + end = pfn_to_page(pfn1) + 1; +#endif
This problem actually exists without sparsemem, too. Discontigmem (at
least) does it as well.
The x86 version of show_mem() actually manages to do this without any
#ifdefs, and works for a ton of configuration options. It uses
pfn_valid() to tell whether it can touch a given pfn.
Long-term, it might be a good idea to convert arm's show_mem() over to
use pgdat's like everything else. But, for now, you should just be able
to do something roughly like this:
- page = pfn_to_page(pfn1);
- end = pfn_to_page(pfn2 - 1) + 1;
-
- do {
+ for (pfn = pfn1; pfn < pfn2; pfn++) {
+ if (!pfn_valid(pfn))
+ continue;
+ page = pfn_to_page(pfn);
+
total++;
if (PageReserved(page))
reserved++;
else if (PageSwapCache(page))
cached++;
else if (PageSlab(page))
slab++;
else if (!page_count(page))
free++;
else
shared += page_count(page) - 1;
page++;
- } while (page < end);
+ }
That should work for sparsemem, or any other crazy memory models that we
come up with. pfn_to_page() is pretty quick, especially when doing it
in a tight loop like that.
-- Dave