On 07/26/2016 05:08 AM, zhongjiang wrote:
From: zhong jiang <zhongjiang@xxxxxxxxxx>
when walking the zone, we can happens to the holes. we should not
align MAX_ORDER_NR_PAGES, so it can skip the normal memory.
In addition, pagetypeinfo_showmixedcount_print reflect fragmentization.
we hope to get more accurate data. therefore, I decide to fix it.
Can't say I'm happy with another random half-fix. What's the real
granularity of holes for CONFIG_HOLES_IN_ZONE systems? I suspect it can
be below pageblock_nr_pages. The pfn_valid_within() mechanism seems
rather insufficient... it does prevent running unexpectedly into holes
in the middle of pageblock/MAX_ORDER block, but together with the large
skipping it doesn't guarantee that we cover all non-holes.
I think in a robust solution, functions such as these should use
something like PAGE_HOLE_GRANULARITY which equals MAX_ORDER_NR_PAGES for
!CONFIG_HOLES_IN_ZONE and some arch/config/system specific value for
CONFIG_HOLES_IN_ZONE. This would then be used in the ALIGN() part.
It could be also used together with pfn_valid_within() in the inner loop
to skip over holes more quickly (if it's worth).
Also I just learned there's also CONFIG_ARCH_HAS_HOLES_MEMORYMODEL that
affects a function called memmap_valid_within(). But that one has only
one caller - pagetypeinfo_showblockcount_print(). Why is it needed there
and not in pagetypeinfo_showmixedcount_print() (or anywhere else?)
Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
---
mm/vmstat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index cb2a67b..3508f74 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1033,7 +1033,7 @@ static void pagetypeinfo_showmixedcount_print(struct seq_file *m,
*/
for (; pfn < end_pfn; ) {
if (!pfn_valid(pfn)) {
- pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
+ pfn = ALIGN(pfn + 1, pageblock_nr_pages);
continue;
}
--
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