On Fri, Nov 18, 2011 at 05:43:10PM +0100, Marek Szyprowski wrote:
From: Michal Nazarewicz <mina86@xxxxxxxxxx>
diff --git a/mm/compaction.c b/mm/compaction.c
index 6afae0e..09c9702 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -111,7 +111,10 @@ skip:
next:
pfn += isolated;
- page += isolated;
+ if (zone_pfn_same_memmap(pfn - isolated, pfn))
+ page += isolated;
+ else
+ page = pfn_to_page(pfn);
}
On Mon, 12 Dec 2011 15:19:53 +0100, Mel Gorman <mel@xxxxxxxxx> wrote:
Is this necessary?
We are isolating pages, the largest of which is a MAX_ORDER_NR_PAGES
page. [...]
On Mon, 12 Dec 2011 15:40:30 +0100, Mel Gorman <mel@xxxxxxxxx> wrote:
To be clear, I'm referring to a single page being isolated here. It may
or may not be a high-order page but it's still going to be less then
MAX_ORDER_NR_PAGES so you should be able check when a new block is
entered and pfn_to_page is necessary.
Do you mean something like:
if (same pageblock)
just do arithmetic;
else
use pfn_to_page;
?
I've discussed it with Dave and he suggested that approach as an
optimisation since in some configurations zone_pfn_same_memmap()
is always true thus compiler will strip the else part, whereas
same pageblock test will be false on occasions regardless of kernel
configuration.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +----<email/xmpp: mpn@xxxxxxxxxx>--------------ooO--(_)--Ooo--
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